摘要:

2866 DOBSON : CCCXCVI1.-The Partial Pressures of Aqueous Ethyl Alcohol. By H~YARD Jom EQLINTON DOBSON. IN connexion with work now in progress it became necessary to have accurate data for the partial vapour pressures of ethyl alcohol at 25" for aqueous mixtures containing up to 90% of alcohol. The system is in itself of obvious importance yet the existing data, for these properties seem t o be defective. Foote and Schole THE PARTIAL PRESSURES OF AQUEOUS ETHYL ALCOHOL. 2867 ( J . Amr. Chm. Soc. 1911 33 1309) obtained figures for the aqueous partial pressure which exhibit a curious break in sequence; this they ascribe to experimental error. Wrewski working at 39.7" (2. physikul. Chem. 1912 81 l) obtained similar discon-tinuities in the same region between 20 and 40% alcohol.The system has therefore been newly studied by the method indicated below; the results prove to be free from the anomalies hitherto prevalent and are believed to have considerable accuracy. Method.-The partial pressures were measured by the d p m i c or ''bubblmg" method. This method consists essenthlly in meaewhg the maw and composition of the mixed vapour which at 25" saturates a measured volume of a chemically inert gas and FIG. 1. FIG. la. thence calculating with the aid of the simple gas laws the partial pressures or more accurately the vapour concentrations of the two componenfs alcohol and water. With some of the higher strengths of alcohol the mass and the composition of the vapour were m d si.multaneously but it was generally found more convenient fo determine these separately for a given aqueous alcohol mixture.The determination of vapour composition is first described and secondly the determination of the mass of vapour saturating a measured volume of gas. Vapur Cmposition.-Nitrogen gas was saturated with the vapour of aqueous alcohol contained in a system of bubblers immersed in a thermostat electrically regulated at 25" & 0.02". The saturated vapour was then carried from the thermostat without condensation through an electrically heated tube E (Fig. l) to a U-tube immersed in a powerful refrigemat and in this U-tube the vapour was quanti 2868 DOBSON : tatively condensed. The composition of the distillate was deter-mined pyknometrically by the special means mentioned below. Since for this purpose as much as 3 grams of liquid had to be distdled it was essential to emure that the change in composition of the final saturating bubbler was negligible.This was achieved by placing a slightly stronger alcohol mixture in the first bubbler, A in which most of the evaporation occurred; the chilling due to latent heat was taken up in the long glass tube B; whiLst the remaining concentration changes were taken up by the second saturator C containing the same liquid as was in the k a l saturator, D. This was specially designed to remove all danger of spray being carried over from bursting bubbles; the absence of spray from this bubbler was proved in special experiments with highly coloured dyes. The exposed tube E was covered with asbestos on which Nichrome wire was wound and a temperature of 80-100" was maintained electrically throughout the experiment.An external glass sheath was sealed to E so that the heating coil exfended below the level of the water in the thermostat. The U-tube proved very efficient in condensing the vapour quanti-tatively; and liquid air used in many of the experiments appeared to have little advantage over a mixture of carbon dioxide snow and ether as a refrigerant for this purpose. The U-tube was 2 feet in total length and was placed in a correspondingly large Dewar flask filled with refrigerant and the distillation was made (generally over-night) in a current of nitrogen flowing a t the rate of 1 to 3 litres per hour. Special precautions were taken and mechanical indicators were devised which showed when any mishap had occurred.All determinations were in duplicate. When sufficient con-densate had been obtained the U-tube was removed from the Dewar flask and the pyknometer (Fig. la) was fitted by the ground glass joint J to the sampling tube F. When the condensate had thawed, and had been thoroughly shaken in the U-tube (to nullify fractiona-tion) it was forced by air pressure into the bulb of the pyknometer to the mark H. The tap was then turned so as to close the bulb, and to connect the joint J to the side tube I. A rubber cap was slipped over J and the pipette was immersed in the thermostat a t 25". When equilibrium was attained excess of alcohol was absorbed by spills of filter-paper till the meniscus stood a t the mark H.The pyknometer was now dried and before weighing it the passage through the tap was washed out from I to J by sucking 30% alcohol through and drying the passage with a current of air. In this way weighings reproducible to 0-2 mg. were obtained, giving densities agreeing within less than 0.0o01 unit. Densities The method of sampling was as follows THE PARTIAL PBESSURES OF AQUEOUS ETRYL ALCOHOL. 2869 a t 25" were used throughout for the estimation of percentage com-position. This waa read from the smooth curve obtained by p l o w on a large scale the accurate data of Osborne and McICelvy (Landolt-Bornstein-Roth " Tabellen," 1923 Ed. p. 448). TABLE I. The Vapow of Aqueous Alcohol. Liquid. @5' 0-986 18 0-97701 0.96572 0.96337 0.94360 0.93285 0.90890 0.89512 0.86068 0.84392 0.81337 4- ' Weight yo alcohol in liquid.6.21 12.36 20-51 28.40 33-90 39.32 50-46 56-50 71.09 78-07 90.12 in vapour. 35.80 54.20 66-17 72.9 1 75-38 77-10 80.03 81.23 84.40 86.20 91.90 Condensed vapour. d y . 0.93990 0.90045 0-87241 0.85634 0.85038 0-84634 0-83903 0.83614 0.828 14 0-82341 0.80860 Error of weight yo 0.03 0-04 0.03 0.01 0.04 0.06 0.02 0-04 0.01 0.03 0.02 figures. Temp. of condensetion of vapour. - 190° - 190 - 190 - 80 - 190 - 190 - 80 - 190 - 80 - 80 - 190 The results of these determinations are in Table I and each is the mean of two or more experiments. The maximum deviation from the mean figure for each concentration is expressed in the fifth column and shows the uncertainty in the percentage compositions.That these figures give a smooth vapour composition curve is shown in Fig. 2 in which these results a*re compared with the previous data of Foote and Scholes which are here represented by crosses on a broken line. Partial Pressures.-The apparatus used was a modification of that employed by Dobson and Masson (J. 1924,125 673) in measuring the aqueous vapour pressure of hydrochloric acid. A current of nitrogen gas saturated with the vapour of the aqueous alcohol at 25" passed through a weighed bubbler containing about 50 g. of concentrated sulphuric acid in which both the aqueous and the alcoholic vapours were quantitatively condensed (Masson and McEwan J .SOC. Chem. Id. 1921 40 2 9 ~ ) . The device used for collecting the issuing gas a t atmospheric pressures has been cGLrettdy described (Dobson J. 1924 125 1968) ; it materially increased the accuracy of the experiments since it maintained in the saturator a constant total pressure which was measured by a manometer. The importance of measuring this quantity has been emphasised by Berkeley (Nature 1918 95 54). Foote and Scholes were apparently able to neglect this through the arrangement of their apparatus and on this account the method of calculation materially differs from theirs. The volume of nitrogen v saturated at 25" with the vapour i 2870 DOBSON : related by equation (1) to the volume V collected in the aspirator and measured at a temperature To absolute and a pressure.B - h, where B is the barometric height and h the vapour pressure of water a t the temperature of the aspirator To. where B is the total pressure in the saturator measured by the manometer and p = p + p& is the total vapour pressure of the mixture which must be estimated by successive approximations. FIG. 2. The uapour compo8ition of aqueoua alcohol at 25'. v = 298*1V(B - h)/{T(B - p ) > . . . . (1) 20 40 60 80 100 Weight yo of alcohol in Zipid. 0 Expe&wntaZ points here determined. x Found by Foote and Scholes (1911 loc. cit.). I n no m e were d u p l h t e experhenb auficiently divergent to be shown by sepamte points on the scale of this figure. The volume v is saturated a t 25" by m grams of vapour having a composition x% alcohol as given in Table I.Taking the molecular weights 18.02 and 46.06 for water and ethyl alcohol respectively we obtain from the simple gas laws the following equations for the partial pressures : (2) V(B - h) loo . . * 3462 mT(B - p ) 100 - x x p* THE PARTIAL PRESSURES OE' AQUEOUS ETHYL ALCOHOL. 2871 Kendall ( J . Amer. Chern. Sw. 1920 42 2481) has shown that saturated steam a t 100" obeys van der Waals's equation when the comtanb a and b are deduced from the critical data. Calculation then shows that the deviation of saturated water vapour from the perfect gas laws amounts to only 0.03% a t 25". A similar calcu-lation for saturated ethyl alcohol vapour a t the same temperature shows that the gas laws hold within 0.1%. The accuracy of the equations is therefore as great as that of the experimental data.The experimental figures a m given in colnmns 2 to 7 of Table 11. With the aid o€ equations 2 and 3 the partial pressures of aqueous and alcoholic vapour pw and p, have been calculated and are given in columns 8 and 9. TABLE 11. Experimental partial pressure results. Pressure in millimetres of mercnry. Wt. % alcohol. lldass c . c-'- in Vol. ** Absolute." " Relative.'' Liquid. z. rn. 7. !.?Oabs. B - h . B,. PI. p d ~ . pa. pr. me. Vapoar. grams. litres. - 0 0 0.3449 15.10 293.9' 738.4 778.4 23.75 - - - -0.4638 20.31 293.9 739.5 779.5 23.75 - - - -12.36 54.20 0.6107 12-24 292.5 742.2 764.4 22.80 10.55 - - -0-7888 16.00 293-2 740.3 763.2 22.60 10.46 23-80 22-55 10.44 0.7454 15.10 293.9 738-4 762-1 22-71 10.51 23-75 22.71 10.51 20.51 66.17 0.9739 15.41 297.1 736.8 766.0 21-72 16-61 23.77 21.70 16.60 14427 16-10 294.1 732-0 755.9 21-87 16.73 23.78 21-84 16.n 1.0366 16.14 293.8 731-3 754.9 21.65 16-56 23.51 21.87 16-73 38-40 72-91 1.6580 20.30 285.8 7494 768.3 21.17 22.29 23-74 21.18 22.30 1.6316 20.33 286.7 735-8 763.3 21.11 22-22 23-n 21-15 '22.26 33-90 75.38 1.4092 16-49 294.3 737.8 762.7 20.83 24.95 23.77 20.81 24.93 1-3859 16.35 594.3 73543 762.2 20.71 2479 23.68 20.77 24.86 1.2826 15-00 294.5 738.2 762.4 20.84 24-95 - - -39.32 77-10 1.4590 16-37 296.7 '132.2 754.1 20-24 26-65 23-45 20.50 26.99 14367 16.10 297.5 731.9 754.7 20-34 26.79 - - -2.7841 31-10 294-7 741.9 761-1 20.13 26-50 23-43 20.39 26-84 1.4935 16.15 292.0 746.5 763-0 20-55 27.07 23.73 20.56 27.09 50.46 80.03 2.0296 20.31 293.9 739.5 765.4 19.63 30.77 23-75 19-63 30.77 2.0229 20-33 293.7 735.6 760-5 19.50 30-57 23.59 19-63 30-78 2-0348 20.33 393.6 7374 762.8 19-62 30.76 23-80 19-58 30.70 56.50 81.23 1.5886 15.02 590.5 747.2 760.7 1846 32.09 23.85 19.04 32.22 1-7458 16.36 289-0 749.7 763.3 19-04 32.22 23-86 18-95 32-07 2.9705 28.26 292.4 732.0 7484 1944 32-22 - - -71-09 84-40 2-3037 20.31 293.7 738.8 763-6 17-28 36.56 23-74 17.29 36-58 2.3741 20.32 288.4 741.0 761.5 17.37 36-77 - - -78.07 86.20 3.2033 26.18 291.3 745-5 764.5 16.19 39.56 23.63 16.27 39.76 1.8569 15.30 292-7 728.2 145.4 16.08 39.28 - - -90.12 91-90 1.9786 14.45 293-7 728-4 746.7 10.66 47-31 23-66 10.70 47-49 2.1785 16.15 296.7 730-1 752.1 10-67 4735 W70 1069 4745 100 100 4 .n ~ ~ 29.70 292.3 746.0 759.3 - 69-01 - - -~~~~ 1) (2) (3) (4) (5) (6) (7) (s> (9) (10) 01) P I As in the experiments of Dobson and Masson (loc. cit.) a simul-taneous determination was made of the vapour pressure of pure water figures being obtained for the mass of water saturating the =me volume of gas a t a total pressure B, measured by a second manometer. Using an equation similar to equation 2 (in which 2 of come becomes zero) figures were obtained for po the vapou 2872 DOBSON pressure of pure water and these constitute column (10) of Table 11. These figures provide not only a measure of the accuracy of the experiment but taking the standard mean value po = 23.75 mm. at FIG. 3. l ’ h e partial pressurea of aqueow alcohol at 25’. 25” they yield an independent measure of the vapour pressures relative to that of water at the same temperature.The “ relative ” partial prwures so obtained are given in columns 11 and 12 of Table 11. In calculating the mean values of these experiments both ’’ rela THE PARTIAL PRESSURES OF AQUEOUS ETHYL ALCOHOL. 2873 tive ” and “ absolute ” figures were considered to be of equal value, and these mean partial pressures together with the total vapour pressures and the vapour compositiom are given in Table 111. The vapour pressure resulb have been ,plotted graphically in Fig. 3 in which they are compared with Foote and &holes’s resulb. TABLE 111. Weight yo alcohol T-T-liquid. vapour. 5. 0 0 6-21 35-80 12-36 54.20 20.51 66-17 2840 72.19 33-90 75-38 39.32 77.10 Vapour pressures in millimetres.7-Aque- A~co-ous. holic. Total. 23.75 - 23-75 22.67 10.50 33.17 21-78 16-66 38-44 21.15 22.27 43.42 20.79 24.90 45.69 20-36 26.85 47-21 - - -Weight yo alcohol in in liquid. vapour. 50-46 80.03 56-50 81.23 71-09 84.40 78.07 86.20 90.12 91-90 X. 100 100 Vapour pressures in millim0tl-M. -7 Aque- A~co- ow. holic. Total, 19.60 30.73 50-33 19.01 32-16 51-17 17-31 38-64 53.95 16.18 39.63 55.71 10.68 47-40 68.08 - 59-01 69.01 Discussion. It appears that these experimental results difEer essentially from those of Foote and Scholes in the measurement of the composition of the vapour. For when these authors’ figures for partial pressures are recalculated using vapour compositions interpolated from the present data instead of from their own the resulting figures for the partial pressures fall in almost every case on the smooth curves of Fig. 3. Foote and Scholes (h. cit. p. 1317) used an analytical method in which the alcohol content of the vapours was determined by combustion over copper oxide the percentage of water in the vapour being estimated by subtracting from the total water pro-duced 3/2 g.-mols. for each g.-mol. of carbon dioxide weighed. In spite of the analytical care displayed by these workers it appears that inaccuracies were liable to occur especially where the water content of the vapour was low. The author wishes to express his indebtedness to Professor Irvine Masson for the interest he has taken in this work and for much helpful criticism and advice. THE UNIVERSITY DUR,E~AM. [Received October 318& 1926.

ISSN:0368-1645    

DOI:10.1039/CT9252702866

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

2874 BRADY AND PERRY: CCCXCVII1.-The Methykction of the Oximes of Bend.* By OSCAR L. BRADY and €€ILDA M. PERRY. THE methyl ethers of the oximes of benzil were investigated by Auwers and Meyer (Bw. 1888 21 3510) and by Dittrich (Ber., 1890 23 3589) both of whom prepared them by the action of methyl iodide on the sodium salts. The former obtained from a-benzildioxime two compounds corresponding in composition to the methyl ethers a (m. p. 165") and a2 (m. p. 109-110") and from p-benzildioxime the ethers p (m. p. 72") and p2 (m. p. 88'). Very little seems to be known of the constitution of these ethers, although Beilstein (" Organische Chemie," 3rd ed. Vol. III 291, 293) assigns to a2 and p2 the structure of 00-dimethyl ethers, C1,Hlo(N*O-CH3),. Auwers and Meyer did not think that orl and p were true dimethyl ethers of benzildioxime.Dittrich obtained from a-bemilmonoxime a methyl ether A, (m. p. 62-63') and from y-bemilmonoxime an ether rl (m. p. 64-65') which he regarded as O-ethers. Investigating the methyl ethers of the benzildioximes he suggested that a and a2 were MeO=N:CPh*CPh:N*OMe and MeO*N:CPh*CPh-NMe respectively. From y-benzildioxime by methylation he obtained the ether p2, formed by isomeric change of the oxime during the reaction. On the other hand Beilstein (op. cit. 4th ed. Vol. VII 760 762) while accepting Dittrich's view of the constitutions of a and p1 a~ the result of a private communication from Auwers assigns to a2 and ps the constitutions CR( :NMeO)*CR( :NMeO). The whole problem has now been reinvestigated methyl sulphate being used as the methylating agent.The constitutions of the ethers have been established by heating them with hydriodic acid and determining the methyl iodide obtained from the O-ethers and detecting the methylamine from the N-ethers by Valton's method (this vol. p. 40). On the Hantzsch-Werner theory a- benzildioxime should give three methyl ethers p-benzildioxime three a-benzilmonoxime two, and y-benzilmonoxime two. Of these ten eight have now been characterised. \O' The results are summarised as follows : * The usual con@prations are adopted for the oximes and not those suggested by Meisenheher (Ber. 1921 54 3206 ; 1924 57 276 282 289) THE ME!l!HYIATION OF THE OXJXES OF BENZIL. 2875 Phs-fj-Ph N-OH HO-N a-Benzildioxims J.J. Ph- ' Q.Ph Ph*fi-fi*Ph Phmfi-fi-Ph $*OMeMeO.k a1 Me*N:O Me0.N a2 Me*N:O O:N-Me OS a-Benzildioxime 00-di- a-Benzildioxime ON-di- a-Beddioxime NN-di-methyl ether methyl ether methyl ether, m. p. 16+165". m. p. 109-110°. m. p. 192". Phmm-Ph HO-N N-OH ~-Benzildioxime J. Ph*R-g-Ph + Ph*R-fi*Ph + P h * m * P h MeO-N N*OMe O:N*Me N-OMe p2 O:NMeMe*N:O fi-Benzildi~xime 00-di- &BenZildioXime ON-di- unknown. methyl ether methyl ether, m. p. 72-73'. m. p. 102-103°. Ph#-COPh N-OH a-Bendmonoxime + N-OMe A1 Me-N:O P h - P O P h .c. P h * p O P h a Bendmonoxime 0-methyl ether u*own. m. p. 60". P h - P O P h y -Bemilmonoxime HO-N 4. P h * p O P h 4. P h - w O P h Me0.N r1 O:N-Me r2 y-Bendlmonoxime 0-methyl ether y-Benzilmonoxime N-methyl ether, m.p. 109-110O. m. p. 63-64O. y-Benzildioxime on methylation gave an oil from which were isolated y-benzilmonoxime U-methyl ether and benzil; the former was probably formed by the hydrolysis of an ON-dimethyl ether, and the latter from an NN-dimethyl ether as the N-methyl com-pounds are hydrolysed with unusual ease. On boiling with concentrated hydrochloric acid a-benzildioxime NN-dimethyl ether gives benzil and a- benzildioxime ON-dimethyl ether gives y-benzilmonoxime 0-methyl ether probably through z-bemilmonoxime O-methyl ether the latter being converted into VOL. CXXVTZ. 5 2876 BRADY AND PERRY : the former under these conditions; whilst p-benzildioxime ON-di-methyl ether gives y- benzilmonoxime U-methyl ether. a - B e d -dioxime 00-dimethyl ether on heating with concentrated hydro-chloric acid in a sealed tube at 110" gives P-benzildioxime 00-di-methyl ether.These results are such as would be expected and the observations of Auwers and Meyer and of Dittrich are brought into line with the usual behaviour of the ethers of the oximes : The 0-ethers are exceptionally stable to hydrolysing agents whereas the hT-ethers are readily hydrolysed ; the latter form hydrochlorides, the former do not; and the P-forms of the dioximes and the y-forms of the monoximes are the most stable at high temperatures. Moreover the formation of 0-methylhydroxylamine ammonia and LV-methylhydroxylamine observed by these workers is in agreement with the results now obtained. The confusion in the literature of these compounds has thus been abolished but the desire to obtain the complete series of ethers has been disappointed.In the experimental part are described attempts to prepare the missing ethers by using other methylating agents and various conditions of methylation. EXPE R I M E N TAL.* Alethylation of y-BenziZmonoxime.-The oxime (10 g.) was dis-solved in sodium hydroxide (10 g. in 120 c . ~ . of water and 5 c . ~ . of methyl alcohol) and to the filtered solution methyl sulphate (18 g.) was added in small portions rise of temperature being avoided. The oil which separated was dissolved in ether and light petroleum added; an oil then separated. The whole was placed in a freezing mixture and after five minutes' scratching the oil solidified. In subsequent preparations rapid crystallisation was induced by inoculation.The solid crystallised twice from boiling ligroin gave y-benzilmonoxhe N-methyl ether in colourless needles, m. p. 109-110" (Found N 5.9. Cl,H1,O,N requires N 5.9%). It was sparingly soluble in ligroin or light petroleum and easily soluble in ether benzene or alcohol. Boiling with hydriodic acid gave no methyl iodide but methylamine was detected by decolor-ising the solution with sulphur dioxide making it alkaline with sodium hydroxide and distilling into alcoholic 2 4-dinitrochloro-benzene when 2 4-dinitromethylaniline was obtained (Valton Zoc. cit.). The ether-light petroleum mixture (above) was evaporated at room temperature the residual oil dissolved in the minimum of * It is important that dl ethereal extracts should be dried before further treatment and that only anhydrous sodium sulphate should be u88d for this purpose THE METHYLATION OF THE O P I ~ S OF BENZIL.2877 ether and hght petroleum added whereby a further quantity of the AT-ether waa precipitated. The filtrate on evaporation yielded an oil which solidified on treatment with a few drops of alcohol and scratching; this having been pressed on a porous tile and c r y s m twice from alcohol y-bemilmonoxime U-methyl ether wm obtained m. p. 63" (Dittrich gives W 5 " ) . Methoxyl determinations made to confirm the constitution of this compound gave consistently low results in presence or absence of acetic anhydride (MeO 7.9 8.6 7.9. Calc. 1Me0 13.07;). As the compound is somewhat readily volatile at loo" a deter-mination wm carried out very slowly by heating fmt for an hour a t 100" with the stream of carbon dioxide sfopped and then a t 135-140" as usual but the result was worse (MeO 7.4%).The heating with hydriodic acid was then carried outin a sealed tube, but a low result was again obtained (MeO 8.2%). The compound was apparently pure it consisted of well-formed transparent crystals which seemed homogeneous under the microscope and remained unchanged in m. p. after crystallisation from various solvents. Dittrich obtained satisfactory analytical Sgures for carbon and hydrogen and these have been confirmed (Found: C '76.5; H 5.5; N 5.9. Calc. C 76.3; €I 5-4; N 5.9%). In view of the possibility that the substance might contain the isomeric AT-ether the hydriodic acid solution from the methoxyl determin-ation was examined by Valton's method (loc.cit.) but methylamine was not detected. Since the substance should contain some 30% of the N-ether to account for the low methoxyl value and more than 0.3 g. of it was employed in the methoxyl determination the amount of methylamine which would have been formed corresponds to 0.03 g. of methylamine hydrochloride; Valton's method will detect 0-005 g . of this compound. Moreover no dSculty waa experienced in detecting a similar amount of methylamine formed in the methoxyl determinations of the ON-dimethyl ethers of benzildioxime. Now y-benzilmonoxime O-methyl ether is the stable isomeride a-bemilmonoxime O-methyl ether paasing into it on heating a t 100" with concentrated hydrochloric acid.It will there-fore be the h t product formed when a-benzihonoxime O-methyl ether and a- and p-benzildioxime ON-dimethyl ethers are heated with hydriodic acid (since the N-methylhydroxylamino-group is very easily eliminated in the last two cases); it is noteworthy that in these cams also similar low methoxyl values were obtained. I f the O-methylhydroxylamino-groups are removed one at a time from the benzildioxime 00-dimethyl ethers y-bendmonoxime O-methyl ether will be iormed and this probably accounts for the low but better methoxyl values obtained with these compoullds. f i E 2878 BRADY AND PEBBY : If Meisenheimer'a configuration (loc. cit.) be adopted a possible explanation can be suggested involving reduction of the carbonyl group and ring formation by elimination of water from the resulting CH*OH and the methyl group.This point is being investigated. P h - F O P h Ph*rCHPh*OH Ph$-yHPh N*OMe + N-OMe -+ N-0-CH, Fortunately in spite of this cMiculty the methoxyl determin-ations leave no doubt of the constitutions of the different ethers. Methylation of a- Bemilmonoxime.-a-Benzilmonoxime wits methyl-ated in a similar manner as the y-compound and the oil which separated was removed with ether. Part of the extract on evapor-ation gave an oil which solidified on scratching (m. p. 54-48'); to the rest light petroleum was added until a faint turbidity was produced and the solution left in a freezing mixture for 10 minutes, when some crystals separated (m. p. 54-58"). The mother-liquor was evaporated at room temperature; an oil was then obtained which solidified on scratching (m.p. 56-59'). No lowering of melting point occurred on mixing the various fractions so if the second methyl derivative is formed the amount must be very small. Two crystallisations from methyl alcohol gave a - b e d -monoxime (;'-methyl ether m. p. 58-59' (Found MeO 8-7 8.5. Catlc. 1Me0 13.0%). Further search was made for the N-ether by distilling the mother-liquor from the first crystallisation in steam t o remove the 0-ether and extracting the residue with ether, but only a very small quantity of a red uncrystallisable oil was obtained. a-Bemilmonoxime 0-methyl ether was boiled for 30 minutes under reflux with concentrated hydrochloric acid. The y-benzil-monoxime 0-methyl ether obtained on diluting the solution and extracting with ether was identified by the method of mixed melting Preparatioi.2 of a- Benzddiozim e.-This oxime is best prepared by dissolving sodium hydroxide (80 g:) in water (500 c.c.) and adding, with cooling a solution of hydroxylamine hydrochloride (40 g.in 100 C.C. of water) followed by finely powdered benzil (50 g.) and alcohol (25 c.c.). After 3 days the small amount of unchanged benzil wits filtered off and the oxime precipitated with carbon dioxide and extracted three times with boiling alcohol in which the a-dioxime is almost insoluble. The residue melted at 230" and was considered sufficiently pure. 2ClethylQ;t;~on of a-BenziZdioxdme.-The oxime (10 g.) was dissolved in sodium hydroxide (30 g.in 200 C.C. of water) with the addition of a little methyl alcohol (5 c.c.). To the filtered solution methyl points sulphate (42 g.) was added in small portions with shaking and cooling. An oil separated which slowly became pasty; this was collected and treated with a small quantity of ether when a solid remained undissolved m. p. 162". Two crystallisations from alcohol gave a fine crystalline compound m. p. 165-166"; further crystal-lisation from alcohol did not raise the melting point. In a Zeisel estimation silver iodide waa produced in amount corresponding to 6.2% of OEt (Half a molecule of alcohol of crystallisation requires OEt 7.7%); but the production of silver iodide may be due to contamination with 0-methyl ether. The substance on crystal-lking three times from benzene gave large colourless crystals, requires N 9.1; loss 12.7%).On heating for 3 hourg a t lOO", the cryatals became opaque and a-benzildioxime "-dimethyl ether was obtained m. p. 192" (decomp.) (Found N 10.5. C16H,,0&, requires N 10.4%). Neither of these compounds gave any alkyl iodide on heating with hydriodic acid. The association of solvent of crystallisation was not unexpected in view of the general tend-ency of the 2C'-ethers of the aldoximes to separate with water of crystallisation. The NN-dimethyl ether is sparingly soluble in all ordinary solvents ; it dissolves in concentrated hydrochloric acid in the cold and on boiling the solution benzil is formed. The alkaline solution from the methylation was extracted with ether and the extracf added to the ether washings obtained in the preparation of the above compound.After removal of the solvent at room temperature an oil containing crystals of the NN-dimethyl compound was obtained. The oil was decanted off the crystals were washed with a little alcohol and the washinga added to the oil. The solution so obtained was evaporated somewhat and con-centmted hydrochloric acid added drop by drop until the whole combfed of a pasty mass which was sucked as dry as possible. The hydrochloride waa washed several times with concentrated hydrochloric acid and finally with warm ether the ether washings being retained (A). The solid was decomposed with concentrated aqueous ammonia; a pasty mass waa then formed which slowly solidified.Crystallised three times from light petroleum it gave a-benzildioxime NO-dimethyl ether m. p. 109". This is apparently the compound m. p. 109-110" described by Auwers and Meyer (loc. cit.) (Found MeO 9.0 9.4. Calc. 1Me0 11.6%). Methyl-amine was detected in the hydriodic acid after the methoxyl deter-mination. a-Benzildioxime NO-dimethyl ether was boiled with concentrated hydrochloric acid for 30 minutes and the mixture was diluted, and extracted with ether. Removal of the solvent gave an oil m. p. 185" (Found N 9.4; lOSS a t looo 12.7. C16E16O$?,,&C6H 2880 RRADY AND PERRY : from which crystals separated. After two crystdlisations from alcohol these proved to be y-benzilmonoxime 0-methyl ether the :N(CH3):0 group having been removed and the 0-ether of the a-monoxime converted into that of the 7-monoxime a change which has been shown to occur under the conditions of the experiment.The ether washings from the hydrochloride (A) were evaporated and the residue was distilled in steam. The small amount of oil which volatilised partly solidified on keeping and the solid on crystallisation from dilute alcohol gave a-benzilmonoxime 0-methyl ether formed probably by the hydrolysis of the NO-dimethyl ether ; no 00-dimethyl ether could be isolated and little if any of this compound appears to be formed under these conditions of methylation. Auwers and Meyer apparently obtained the 00-dimethyl ether by the action of methyl iodide on the sodium salt of the oxime, but some doubt existed whether their compound m. p. 165" was actually the 00-dimethyl ether or the NX-dimethyl ether con-taining alcohol of crystallisation (m.p. 166"). A methylation with methyl iodide was carried out a simpler technique than that of Auwers and Meyer being used ; a-benzildioxime 00-dimethyl ether, m. p. 161" and a-benzildioxime NO-dimethyl ether were obtained, but no XX-dimethyl ether. A better method of obtaining a-benzildioxime 00-dimethyl ether consisted in mixing a-benzildioxime (2 g.) with dry silver oxide (2 g.) and methyl iodide (2-3 g . ) diluting with dry ether and heating under reflux for 2 hours. The mixture was filtered and the residue extracted twice with hot ether ; on cooling a solid separated from the filtrate. The solvent was evaporated a t room temperature, leaving a solid and a small quantity of oil.The solid was crystal-lised three times from acetone and the a-benzildioxime 00-dimethyl ether described by Auwers and Meyer was thus obtained m. p. 163-164" (Found MeO 18.8. Calc. 2Me0 23.1%). This was identical with the somewhat less pure product (m. p. 161") obtained above. The hydriodic acid solution from the methoxyl determination gave no methylamine when tested by the method described above. Heated in a sealed tube with concentrated hydrochloric acid for 10 hours a-benzildioxime 00-dimethyl either gave an oil; this solidified on scratching and after crystallising from alcohol was identified as p-benzildioxime 00-dimethyl ether. The observation of Auwers and Meyer was thus confirmed. Prepration of p-Benzildioxime.-A much more satisfactory method of preparing p-benzildioxime than that described in the literature consists in dissolving a-benzildioxime in the minimum of freshly distilled boiling aniline ; on cooling (3-benzildioxime con TE~E METHYLATION OF THE OXTMES OF BENZI-L.3881 hining sniline of crystallisation separates. The crystah rtre sucked aa dry aa possible waahed with dilute hydrochloric mid which removes the aniline of crystalliaation then with water and crystal-lised twice from alcohol when the pure @-dioxime is obtained. Metisyksta'on of 8 - Benzildiozime .-@- Benzildioxime was methylated with methyl sulphate in a similar manner as the a-compound and the oil obtained was extracted with m little ether as possible. The extract wm washed several times with 0-2N-hydrochloric acid (to remove a trace of a basic compound which is simultaneously formed), dried and saturated with dry hydrogen chloride; an oily hydro-chloride then separated.The ether was decanted and light petro-leum added. The additional hydrochloride thus obtained was added to the previous material and the whole was washed twice with small quantities of ether; the was- were added fo the main bulk of the ether solution (B). The hydrochloride was decom-posed with concentrated aqueous ammonia. The oil thus obtained W&B washed with water by decantation and left in an evacuated desiccator over solid sodium hydroxide. It slowly became very Viscous and after treatment with ligroin and 10 minutes' scratching it became pasty and h a l l y solid (m. p. 83-89"). The ligroin washings when allowed partly to evaporate at room temperature, deposited crystals (m.p. 88-90"). The solid (m. p. 83-49") w~ba heated with ligroin until it was on the point of melting and the solution was then decanted and inocuIated with a crystal of the above solid (m. p. 8S-9O0). This treatment was repeated with the residual semi-solid material until only a small quantity of dark oil remained. The extracts deposited an oil which solidified on keeping over-night. Fine needles projected from the solidified oil, and these melted at 90-92" and seemed to be identical with the compound m. p. 88-89' described by Auwers and Meyer. On keeping for some time however they became opaque and then melted a t 102-103". The solidified oil on crystallisation from ligroin gave the same product m.p. 102-103" which was p-benzil-dioxime NO-dimethyl ether (Found MeO 10.3. Calc. 1Me0, 11.6%). Methylamine was detected as before in the hydriodic acid from the methoxyl determination. When ~-benddioxim;? NO-dimethyl ether was heated with concentrated hydrochloric acid for hour under reflux and the mixture was cooled diluted, and extracted with chloroform an oil was obtained which partly solidified on cooling in ice and scratching. The solid after p 6 -cation was found to be y-benzilmonoxime 0-methyl ether. The ether-light petroleum solution (B) was evaporated at room temperature and the solid obtained after being freed from oil was crystdlised four times from alcohol ; p-henzildioxim 2882 BRADY AND PERRY METHYLATION OF OXIMES OF BENZIC.00-di-methyl ether wm thus obtained m. p. 72-73" (Found MeO, 21-4. Calc. 2Me0 23.1%). No methylamine was detected in the hydriodic acid residues. Methylation with methyl iodide and sodium methoxide as described by Auwers and Meyer gave the NO-dimethyl ether and the 00-dimethyl ether as above. NethyWtion of y-BenziZdioxime.-The y-dioxime wa8 suspended in sodium hydroxide (15 g. in 100 c.c.) and methyl alcohol (5 c.c.) added followed by methyl sulphate (21 g.) in small portions with cooling. The oil which separated was removed with ether and the extract was washed with 0-2N-hydrochloric acid and treated with excess of light petroleum which precipitated an oil (C). The mother-liquor was evaporated the oil taken up with a little ether, and light petroleum again added; an oil (D) waa precipitated.On decanting the solution and evaporating an oil was obtained which solidified on keeping in an evacuated desiccator for some days. Thh solid after crystallising twice from methyl alcohol was found to be y-bemilmonoxime O-methyl ether. The oil (C) on keeping in an evacuated desiccator for some time partly solidified. It was then pressed on a porous tile and the yellow solid crystallised from ligroin and from acetone and water when benzil was obtained. The oil (D) on keeping deposited crystals of y-benzilmonoxime O-methyl ether but all attempts to obtain a solid from the remain-ing oil were unsuccessful. The formation of b e d and y-bemil-monoxime O-methyl ether suggests that N N - and NO-dimethyl ethers of y-benzildioxime are formed but are very readily hydro-lysed. y-Benzildioxime was boiled in ether with methyl iodide and dry silver oxide and the solution was extracted with 2N-sodium hydroxide to remove unchanged oxime and evaporated. On keeping the oil obtained deposited a few crystals (m. p. 145-157") insufficient for further purification. All attempts to obtain a solid from the rest of the oil were unsuccessful. Atternpi% to Prepare a-Benzilmonoxime N-Methyl Ether and p-Benzildioxime NN-Dimethyl Ether .-a-Bemilmonoxime was treated with methyl sulphate and with methyl iodide without other addition and also in ether with diazomethane. The dry sodium salt of a-benzilmonoxime was boiled with ether and methyl iodide and benzil waa treated with p-methylhydroxylamine under various con-ditions. None of these methods met with success. Attempts were also made to methylate p-benzildioxime with methyl sulphate and with methyl iodide without other addition and in dry acetone solution but no change was observed. THE RALPH FORSTER LABORATORIES OF ORaANIC CHEMISTRY, UNIVERSITY COLLEGE LONDON. [Received J d y 2lst 1926.

ISSN:0368-1645    

DOI:10.1039/CT9252702874

出版商:RSC    

年代:1925

数据来源: RSC

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STUDIES OF DYNAMIC ISODIXBISM. PART XX. 2883 CCCXCIX.-c?tudies of Dynamic Isomerh. Part X X . Amphoteric Solvents as Catalysts for the Muturota-tion of the Sugars. By THOU h m L O ~ Y and I~VINE JOHN FAULKNEB. 1. h the preceding paper of this series (this vol. p. 1385) evidence waa adduced to show that the mutarohtion of the sugars is not due to a mere spontaneous tautomeric change involving only the molecules of the sugar itself but to a molecular rearrangement in FIG. 1. FIG. 2. Mutorotation of tetrmnedhylglucoee (a) in @ine and water @ (b) in @ne and creaol k. Muturotatwn of glucose in pydine andwrrter. 100 80 60 40 20 0100 80 60 40 20 0 "/b P y r idine . which other constituents of the solution also play an essential part. Of the constituents which interact catalytically with the sugar to bring about this rearrangement water is the most im-portant since it waa already obvious in 1904 from Irvine's work on the methylated sugars that the mutarotation is retarded enorm-ously and in some cases may be almost stopped by working in non-aqueous solvents.The opinion was therefore expressed (J., 85 1566) that all the data then available could be interpreted by attributing the mutarotation to a process of " hydrocatalysis " of the sugar. At that time only one assertion could be made in reference ta 5 E 2884 LOWRY AND FAULKNER : the mechanism of this hydrocatalysis namely that since glucose hydrate exhibits just the same mutarotation as glucose itself the change of structure which causes the changes of rotatory power could not take place during the initial hydration of the sugar, but must occur a t some subsequent stage e.g.by a molecular rearrangement or isomeric change in the hydrated sugar. A further consideration of the mechanism of mutarotation (this VO~., p. 1371) especially in comparison with the mechanism of hydrolysb, led however to a much more definite suggestion namely that water probably acted as a catalyst for mutarotation in virtue of the fact that it possesses both acidic and basic properties and that in general the essential condition for the mutarotation of a sugar is that the solvent should possess amphoteric properties. This conclusion has the advantage of providing an explanation of the well-known fact that acids and bases produce even higher velocities of mutarotation than water alone and of the further fact (which was discovered in the come of our own experiments) that pyridine which is a powerful catalyst in the presence of water, is not a catalyst at all for the mutarotation of tetramethyl glucose when used in the absence of water.2. The experiments described in the present paper had their origin in the conception of the mechanism of mutarotation which is outlined above. The most important results of the experiments are to show : (i) That pyridine which is inactive when dry gives when mixed with about twice its weight of water a maximum velocity of mutarotation which is about twenty times as great as the velocity for solutions of the same sugars (glucose and tetramethyl glucose) in pure water.(ii) That cresol like pyridine has no appreciable catalytic properties when water is not present showing that acids and bases may alike be rendered ineffective if used in the absence of water. (iii) That mixtures of cresol and pyridine each sufficiently dry to give only a negligible velocity of mutarotation when mixed in the proportion of about 2 parts of cresol to 1 part of pyridine are again about twenty times as active as water in promoting the mutarotation of tetramethyl glucose. It is of course possible to argue that perfectly dry pyridine and perfectly dry cresol would be incapable of producing muta-rotation; but this criticism even if it could be vindicated by experiments on the effect of extreme drymg would not affect the present discussion since it is clear that n mixture of pyridin STUDIES OF DYNAMIC ISOMERISM.PART XX. 2885 and crew1 is able to do what neither solvent can do by itself namely, to give a velocity of mutarotation which is far greater than in a solvent containing 100% of water. In other words if a trace of water is e-ssential (as it may be even in order to enable the acid and base to interact to form an unstable salt),* the intense activity of the mixed solvent is due to its pronounced amphoteric character, and not to a direct catalytic action upon the sugar of any minute trace of water which it may contain. 3. It is interesting to notice the theoretical conclusions which follow from the experimental facts thus established namely (i) that (just as in the case of nitrocamphor) it is impossible for a profon to wander directly from one position to another within the molecule of the sugar and (ii) that in order to effect this transfer it is neces-sary to provide a medium into which a proton can escape from the sugar and from which a proton can be provided to replace the proton thus lost by the sugar.These conclusions are supported by the fact that the only sub-stances which are now known to act as catalysts for the muta-rotation of the sugars are those which possess either acidic or basic properties or both. Oxygenated solvents such as acetone and ethyl acetate even when used in presence of water retard rather than accelerate the mutarotation; and even their " polar " character and relatively high dielectric constants do not enable them to develop any catalytic activity.The mechaniam of muta-rotation suggested above which involves an interchange of protons between the sugar and the medium (just as in the interaction of an acid and a base) appears therefore to be the only one which is in accord with the experimental facts and no alternative mechanism is yet known which can replace it. E X P E R I M E N T A L . 4. The sugars were the same samples as those used in Part ,YILi. The solvents used were as follows (i) Air-free distilled water. (ii) Pyridine (B.D.H. "Extra Pure") shaken twice with quick-lime for 24 hours and distilled twice shaken with barium oxide and twice fractionated giving about 800 C.C. boiling from 114-8" to 115.2" (corr.) from about 1 litre. The sample gave a residual velocity of mutarotation of tetramethyl glucose not greater than O-OOO4 in minute-units.(iii) o-Cresol (B.D.H. " for cineol-deter-minations ") from R sealed flask was distilled immediately before use; when liquefied by the addition of a little benzene and used * The melting-point curve for pyridine (m. p. -41') and o-cresol (m. p. 30") rises to a maximum at -+-lo in an equimolecular mixture of the acid and base (Bramlcy J. 1916 109 476). 5e* 2886 STODlES OF DYXAMIO ISOMERISM. P U T XX. as a solvent for tetramethyl glucose it gave an arrest of mutra-rotation during a period of 6 hours followed by a slow change with a velocity coefficient of about 0.0005. m-Cresol (B.D.H., specially prepared) was redistilled and gave a velocity coefficient of 0-0003 only. 5.Muturotatkm-curves were plotted as follows One gram of sugar waa weighed out in a 20 C.C. flask and the mixed solvent, previously made up by weight in another vessel was added at zero time. The solution was transferred quickly to an air-dried polarimeter tube (2 dcm.) and readings were taken as soon as possible namely about 2 minutes from zero time in the case of water and pyridine but about 5 minutes in the case of solutions rich in cresol which were much more viscous. 6. The experimental results are summarised in Tables I 11, TABLE I. TABLE 11. TABLE 111. Mutarotation of Tetra-methyl Glucose in Mutarotstion of Tetra-Mutarotation of Glucose in mixtures of Pyrid- methyl Glucose in mixtures of Pyridine and ine and Water at mixtures of Cresol Water at 20".20". and Pyridine at 20". k. % Creaol. k. % H,O- k.* % H*O. 100 95 90 85 80 70 65 60 60 40 30 20 10 0 0.015 0.140 0.258 t 0.274 0.282 0.272 0.269, 0.225 0.277 0.288 0.210 0.190 0-221 0.236 0.166 0-168 0,106 0.100 0-046 0.012 0-0008 0-258 100 97.5 95 92-5 90 85 80 76 70 60 50 40 30 20 10 0 0-0128 0.099 0.177 0.219 0.264 0.261 0.272 0.254 0.267 0-273 0.300 0-317 0-238 0.318 0.291 0.251 0.203 0.179 0.108 0.040 0.042 0.0088 0.0003 100 0.0003 99 0-027 97.5 0.060 95 0-082 92-6 Mutarotation to too rapid for 55.0 measurement. 52.5 0.180 49.9 0.148 40.4 0.067 21.1 0-0168 1-62 0.0013 0 0-0003 k = l / t . (log (ao - a ) - log (q - a )).In calculating this coefficient Values shown in italics correspond with a half-change period of less than $ m-Cresol was used for these four solutions as o-cresol is solid at these the time was always expressed in minutea. 3 minutes and are not regarded as trustworthy. concentrations. and 111 and are represented graphically in Figs. 1 and 2. The individual readings have not been reproduced. A complete muta-rotation-curve is therefore represented by a single monomolecular coefficient $ in the tables and by a single point on the curves. 9 The evidence for the monomolecular character of the curves will be dis-cussed later in another psper BEAUI'IONS OF ORGAXIU TEIWULPHATES. 2887 Even under the moat favourable conditions the fastest muta-rotations for which fairly trustworthy data can be given correspond with a velocity.coefficient of less than 0.2 since this velocity coefficient already corresponds with a half-change period of only 2.3 minutes. Values greater than this are therefore shown in italics in the tables and are indicated only by a dotted line in Figs. 1 and 2. In the case of glucose the mixtures which gave the highest velocities also gave cloudy solutions which were difficult to read; but the general come of the curve can be inferred fairly accurately from the velocity coefficients for stronger and weaker solutions for which much more concordant values were obtained. The mixtures rich in cresol suffered from the two-fold disadvantage that they were very viscous and showed only a relatively small change of rotatory power ; the velocity-concentration curve for pyridine-cresol mixtures therefore includes a longer dotted section than the two curves for mixtures of pyridine and water. We desire to thank the Depa,rtment of Scientific and Industrial Research for a maintenance grant to one of us (I. J. F.) during the period in which this research was carried out. UNIVERSITY CHEM~CAL LABORATORY, CAlKBRIDGE. [Received November Znd 1926.

ISSN:0368-1645    

DOI:10.1039/CT9252702883

出版商:RSC    

年代:1925

数据来源: RSC

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BEAUI'IONS OF ORGAXIU TEIWULPHATES. 2887 CCCC.-Reuctiom of Organic Thiosulphatea. By HENRY BELL FOOTNER and SAMUEL SMILES. ABUNDANT evidence is available showing the instability of the disulphoxides which are to be regarded as containing the thiol-sulphomte structure *S*SO,* (this vol. p. 224) and the ease with which their sulphur chain may be r u p t d . To ascertain whether this type of reaction is exhibited by the thiosulphonate group under other structural conditions the organic sodium thio-sulphates which owing to the work of Price and Twiss (J. 1907, 91 2021) may be confidently assumed to have the thiol-sulphate structure RS*SO,*ONa have been examined. In aqueous solu-tion these substances are very readily decomposed by odium mercaptides and by alkali cyanide.The former reagent quickly yields a t the ordinary temperature sodium sulphite and an in-soluble product composed of a disulphide or a mixture of disulphides, according to the mercaptide used, RS-SO;Na + NaSR = RS-SR' + Na$03. When R and R' axe the same this product is homogeneous and consisfs of a symmetrical disulphide but when they ar 28SS FOOTNER ANT) SMTLES : c2issimilar it is in most cases a mixture of the two possible symmetrical disulphides; only in a few instances has the un-symmetrical disulphide been isolated. This behaviour is closely pamllel to that of the disulphoxides (J. 1924 125 176), RS*SO,R + R’SNa = RS-SR’ + RSOga, and the formation of the mixture of symmetrical disulphides is adequately explained by the secondary reaction of fhe mereaptide with disulphide (Lecher Ber.1920 53 591): RS*SR’ + NaSR GRS-SR 4- R’SNa. The organic thiosulphates are also quickly decomposed by nqucoiis alkali cyanide more than 90% reacting thus : RS*SO$Ta + NaCN = RSCN + Na,SO,. The products are almost pure and the yields being excellent the method is well adapted to the preparation of thiocyanates when the corresponding thiosulphates are available. According in un-published experiments the disulphoxides behave in a similar manner, RS*SO,R + NaCN = RSO,Na + RSCN, but are much less reactive. The interaction of mercaptans and di-p-toluenesulphonyl sulphide (Troger J . pr. Chern. 1899 60 117) has also been examined with similar results, (C,H,=SO,),S + 2RSNa = C,H,*SO,-SNa + C,H,*SO,Na + (RS),, the sulphur chain being ruptured with formation of sulphinate and thiosulphonate together with the disulphide corresponding to the mercaptan used.According then to these experiments and others previously made with disulphoxides the characteristic reactions of the thiol-sulphone group in substances of the type RS*SO,*X are mainly due to instability of the dithio-system; this group is readily split by alkali mercaptides and with varying ease by other reagents, the activity depending on the character of the group X. Experiments have also been made with the polythionates. Sodium dithionate is not attacked by alkali mercaptides but the tri- and tetra-thionates are rapidly decomposed the disulphide being formed in both cases. The trithionate is resolved into sulphite and thiosulphate and the tetrathionate into thiosulphate.The completed reactions, Na,S,O + 2RSNa = (RS) + Na2S0 + N%S,O, Na,S,O + 2RSNa = (RS) + 2Na2S203, may be regarded as analogous to the reduction of these substances by sodium amalgam. Strictly quantitative measurements have no REACTIONS OF ORGANIC THLOSULPHATES. 3889 been made but more than 90% of the materials undergo the reactions indicated. Whilst the constitution of the polythionates is undeter-mined nothing further can be said of the nature of these reactions but bearing in mind the known behaviour of merctmptides with the dithio and thiohulphone systems the processes are in the authors' opinion adequately explained by the structures proposed by Mendelbv for the polythionates. In this comexion the close resemblance of the behaviour of the trithionate to that of ditoluene-sulphonyl sulphide is significant.E x P E R I M E N T A L. Reaction of Organic T h > W p - with Sodium Mercuptidtw-The benzyl and jp-nitrobenzyl thiosulphates used were prepared by Price and Twiss's method (Eoc. cit.) and the 9-anthryl thio-sulphate by Friedlander's (Ber. 1922 55 3969). The sodium mercaptide (1 mol.) and the thiosulphate (1 mol.) reacted rapidly in aqueous solution a t the ordinary temperature. After Q hour, the solution was neutral and contained sulphite with at the most only traces of sulphate. The yield of the precipitated disulphides generally exceeded 95%. The results from six of the cases examined are in the following table : Bemyl. BeIIZyl. Benzyl disulphide 99%.2-Nitrophenyl. Bewl. Benzyl 2-nitrophenyl disulphide, 9-Anthryl. Benzyl. Dianthryl dibenzyl and anthryl 2 - Nitr ophenyl . 4-Nitrobenzyl. 2-Nitrophenyl and 4-nitrobenzyl di-2 5-Dichlorophenyl. 9-Anthryl. Dianthryl and tetrachlomdiphenyl 2 -Ni trophen y 1. 9-Anthryl. 2-Nitrophenyl and anthryl di-The symmetrical disulphides named have been previously de-scribed. Benzyl 2-nitruphenyl disulphide separated from alcohol in yellow needles m. p. 54" (Found N 5.4; S 23.3. C1,HllO~S requires N 5-05; S 23.1%). The melting point of an equimolecular mixture of the two symmetrical disulphides was lowered by admixture with this substance. Benzyl 9-anthryl dkdphide was isolated from warm alcohol in yellow prisms m. p. 128". When it was mixed with equimolar proportions of dibenzyl and dianthryl disulphides its melting point was lowered (Found C 75.5 ; H 4.4; S 19.5.C,,H1&3, R & h of Organic Thiosulphutes with Alkali Cyanide.-On Memaptan. Thiosulphate. Products. 99%. benzyl disulphides. sulphides. disulphides. sulphides. requke~ C 75.9; H 4.8; S 19.3%) 2890 REACTIONS OF ORGANIC THIOSULPHhTES. miXing aqueous solutions of potassium cyanide and the thio-sulphate (equal mols.) reaction quickly ensued. It waa completed by keeping the mixture for various periods generally Q hour Qr was assisted by maintaining the temperature at about 30". The yield of thiocyanate which separated practically pure in most case8 was almost quantitative and a corresponding amount of sulphite was found in the aqueous liquor.In this way the following thiocyanates were isolated. Benzyl thiocyanate m. p. 41" (Found N 9.7; S 21.3. Calc., N 9.4; S 21.5%). 2-Nitrobenzyl thiocyanate m. p. 71" (Found N 14.7. Calc., N 14.4%). Cassira (Ber. 1892 25 3028) gives the m. p. of this substance as 75". 4-Nitrobenzyl thiocyanate colourless prisms m. p. 79" from warm alcohol (Found N 14.1; S 16-4. C,H,O,N,S requires N 14.4; S 16.5%). 9-Anthryl thiocyanute pale yellow needles m. p. 181" from hot alcohol (Found N 6.4; S 13.4. C,,HPS requires N 6.5; S 13.6%). Reaction of Di-p-toluenesUl.phon~l Sulphide with Hermphm.-An alcoholic solution of the mercaptide (2 moh.) and the sulphide ( 1 mol.) containing 5 g. in 100-150 C.C. was warmed on the water-bath and the solvent was then evaporated water being added towards the completion of the process.The insoluble product, in all the cases examined was the disulphide corresponding to the mercaptan taken. The solution containing sulphinate and thiosulphonate was acidified and gently warmed to decompose the latter; after the addition of aqueous sodium carbonate the coagulated sulphur was collected and the filtrate again rendered acid. The liberated sulphinic acid was in each case p-toluene-sulphinic acid. The disulphides obtained in this way from 2 5-dichlorophenyl, 6-methoxy-m-tolyl and 3-chloro-6-methoxyphenyl mercaptans were identified by comparison with authentic samples from other sources. Reaction of Sodium Tetruthion.de with Mermptides.-A typical experiment was as follows. A solution of 5 g .(2 mols.) of 6-methoxy-m-tolyl mercaptan in a small volume of alcohol was exactly neutral-ised with aqueous sodium hydroxide and added to a stirred solution of 7-5 g. (1 mol;) of sodium tetrathionate in 200 C.C. of water. The disulphide separated a t once but the mixture was kept for an hour before the solid WM collected. The filtrate contained thio-sulphate but no sulphite. Determinations of the iodine value were made and the roughly quantitative data obtained agreed well with the equation previously given; e.g. (a) 6-methoxy OBSERVATIONS ON THE CLAI!3EN REACTION. 2891 m-tolyl mercaptan I value 92% ; disdphide 97% of theory, (b) 3-chloro-6-methoxyphenyl mercaptan I value 95% ; di-sulphide 95% (c) 2 5-dichlorophenyl mercaptan I value 98%; disulphide 99%. Reaction of Sodium Trithionate with Mermptam.-The method of experiment was the same as the preceding. With benzyl, 6-methoxy-m-toly1 and 2 5-dichlorophenyl memaptans the di-dphides were isolated in 99-100~o of the yields required by the equation previously given whilat the approximate iodine values of the fltmtm were about 90%. Estimation of the sulphite in the case of 6-methoxy-m-tolyl mercaptan showed 99-100~o of the theoretical amount of this salt to be present in the aqueous liquor. We desk to thank the Department of ScientSc and Industrial Research for a grant which enabled one of us to take part in fhis work. KING'S COLLEGE LONDON. [Received November W 1926.

ISSN:0368-1645    

DOI:10.1039/CT9252702887

出版商:RSC    

年代:1925

数据来源: RSC

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OBSERVATIONS ON THE CLAI!3EN REACTION. 2891 CCCC1.-Observations on the Cluisen Reaction. By GILBERT T. Momm and EUSEBIUS Horns. UNTIL recently the condensation of the higher methyl monoketones with esters under the influence of sodium had only been inve&igated up to the homologues containing the radicals n-hexyl aad n-nonyl. The present investigation wsts undertaken to fmd out where and if possible why the reaction stopped when applied to methyl ketones containing also one of the higher alkyl radicals. The nomenclature throughout this paper is based on the following condemation with ethyl acetate : It is shown that under the conditions stated the reaction proceeds quite normally from 12. = 7 to n = 19 a satisfactory yield of 1 3-diketone being obtained in every case.The general method of procedure has been to convert the cor-reaponding fatty acid into its barium salt and to distil this with three molecular proportions of anhydrous barium acelate in a specially constructed flat vacuum pan (Morgan and Holm- J . Soc. C h . I d . 1925 44 108~). The crude product wa8 p d e d and subjected to the Claisen condensation with sodium and ethyl acetate the sodium salt of the enolic form of the @-diketone being treated with acetic acid and the liberated diketone precipitate 2893 MORGAN ANT HOLMES : and purified aa its co-ordinated copper derivative. The acids C&H,+,*CO$€ where n = 10,12,14 18 were obtained by oxidising the methyl ketone from the next higher naturally occurring acid, to give acetic acid and the required acid from which mixture the lrttter wa8 isolated as its relatively insoluble barium salt.The copper mlts of the @-diketones are blue as are the lower members of the series but the colour becomes less pronounced as the homologous series is wended. The diketones from n = 7 to 19 have been obtained as solids a t the ordinary temperature, whilst the monoketones from ?a = 10 upwards are colourless solids with progressively higher melting points. Since this work originally arose out of the researches on cyclic kllurium compounds of bactericidal potency it is of interest to note that Mr. C. J. A. Taylor (this vol. p. 2615) has found it possible to prepare cydotelluropentanedione dichlorides reducible to bacteri-cidal cydotelluropentanediones in the case of the following diketones, all of which are described in the present paper n-octoylacetone, n-nonoylacetone and n-duodecoylacetone (lauroylacetone).These are the only ones so far condensed with tellurium tetrachloride, but it appears probable that the whole of the series woiild give similar results. E X P E R I M E N T -4 L. In the case of the lower members of the series n = 9 and below, the procedure was as described below in the case of n-octoylacetone. For the higher members three to nine mob. of the ester were employed no preliminary coohg being necessary. After heafing under reflux for from 4 to 5 hours the mixture was poured on to ice as before. The mixtures were then neutralised with acetic acid and satur-ated cupric acetate was run in. In most cases the copper salts of the diketones were precipitated a t once but for the higher ones 72 = 15 and upwards it was found necessary to add alcohol to bring the reagents together.The free diketones were obtained by treating the copper salts with dilute sulphuric acid in the presence of ether which was subsequently removed. The lower diketones were purified by vacuum distillation the higher ones by crystallisation from alcohol. n-Octoylacetone.-n-Heptyl methyl ketone (35 g.) obtained by the dry distillation of barium n-octoate with barium acetate (3 mols.) was added to ethyl acetate (2.5 mols.) the mixture cooled to O" and sodium (1 atom.) added in the form of thin slices. After 12 hours the mixture was heated under reflux for 3 hours allowed to cool and poured on to ice.The liquid was then made ver OBSERVATIONS ON THE CLAISEN REACTTON. 5893 slightly acid with dilute acetic acid and the oily layer of liberated diketone precipitated with a saturated solution of cupric acetate. After being stirred a t intervals for 4 hour the precipitate was collected and washed with a little water and cold alcohol. A yield of 26 g. represented 4743%. T w o subsequent batches gave yields of 41.0 and aS*6% respectively. Crystam successively from alcohol and benzene the ~olvper salt w&s obtained in pale blue needles and melted a t 118". The salt (0-5 g.) was shaken with a few C.C. of dilute sulphuric acid in the presence of a little ether. The acid layer was separ-ated and a water washing of the ether layer added. The copper was precipitated by means of caustic potash and weighed as the oxide (Found Cu 14.6; C 61.6; H 8.85.C,,H,804Cu requires Cu 14.8; C 61.45; H 8.8%). The n-octoylacetone recovered from the copper salt had the characteristic d o u r of the p-diketones of this series and boiled at 248"/755 mm. and 118"/5 mm. n-NonoylQcetone.-A quantity of the corresponding ketone from a reputed pure specimen of barium pelargonate (23 g.) was added to 37 g. of pure dry ethyl acetate and 3.8 g. of sodium were added to the cooled mixture. The copper salt of a diketone was obtained by the general method and weighed 26.3 g. a yield of 68.8%. Recrystdised from benzene it melted at 107" and was of the expected pale blue colour (Found Cu 13-9. C,E,,O,Cu requires Cu 13.9%). Since the above melting point was not in accord with those of the other members of the series and furthermore other dis-crepancies arose when the diketone was condensed with tellurium tetrachloride another specimen of pelargonic acid was obtained and the reactions were repeated.Again the copper salt of a diketone waa obtained purified and analysed (Found Cu 13-75; C, 63.05; H 9-4. Theory requires Cu 13-9; C 62-9; H 9.2%). "his specimen melted at 11,5.5" a value bringing it in line with its homologues. It appears probable that the earlier specimen of acid contained an acid isomeric with pelargonic acid but having a branched chain remote from the carboxyl group. The n-nonoylacetone recovered from the copper salt boiled a t 150"/15 mm. n-Decoylacetone.-This diketone has been described (Morgan and Holmes J.1924 125 760; J . P k m . Soc. June 14 1924). n- UndecoyEarcetone.-n-Decyl methyl ketone obtained from the corresponding undecoic acid which was itself prepared by the ketone and acidified dichromate degradation of lauric acid, was condensed with sodium and ethyl acetate (6 mob.). Th 2894 MORGAN AND HOLMES: yield of copper salt was 3.9 g. (70%). After crystallisation from benzene the salt melted at 112" (Found Cu 12.4; C 65-6; H, 10.0. C,,Hm04Cu requires Cu 12-4; C 65.4; H 9.7%). The free diketone was obtained as a colourless solid melting at 28". n-Duodeuylucetone (Lauroyhcetone).-Three separate batches of the monoketone obtained from lauric acid were condensed with 3, 6 and 9 molecular proportions of ethyl acetate respectively the period of refluxing being extended to 4 hours.The yields of copper diketone from 5 g . of ketone were 2.6 g. 3.45 g. (50.2%), and 3-40 g. respectively. It appears that the optimum yield of rather more than 50% was reached by using 6-8 molecular pro-portions of ester in the condensation. The pure salt melted at 112.5" (Found Cu 11.7; C 66.6; H 10.3. CsH,O,Cu requires Cu 11.7; C 66.5; H 10.0%). The free diketone wm a colourless solid of melting point 31-32'. n-Tridecoyhetone.-Myristic acid was converted into the barium salt and -distilled with barium acetate. The resulting methyl ketone was then oxidised with acid sodium dichromate to give the next lower acid which on subsequent &illation of its barium salt gave the duodecyl methyl ketone. This (5 g.) was condensed with ester fo give 3.7 g.of the copper dikdone a yield of 54%. The pure salt melted at 111" (Found Cu 11.2. C3,H5,04Cu requires Cu 11.2%). The pure diketone obtained from the copper derivative was a colourless solid melting at 35". It had scarcely any d o u r and gave the red ferric coloration with alcoholic ferric chloride only on warming (Found C 75.4; H 11.7. C1,HSO2 requires C 75-6; H 11.8%). n - T d r w l a c e t o n e (Nyristqyklcetone).-Five g. of the ketone obtained from myristic acid were subjected to the Claisen reaction, giving 3-42 g. of copper salt (yield 52%) which after crystallisation from alcohol and from benzene melted at 112" (Found Cu 10.5. CMHs2O4Cu requires Cu 10.6%). The free diketone melted at 39' (Found C 76.1; H 12.3.C1,H3202 requires C 76.1; H 11.9%). n- Pentcsdecoy laceton e .-n - Tetr adec yl met h y 1 ketone was prepared from palmitic acid by the general degradation process. Condensed with ethyl acetate it gave 2.25 g. of the copper diketone a yield of 35%. The purified salt melted at 111" (Found Cu 10-5. C,,H6,0,Cu requires Cu 10.2%). The colourless diketone melted at 42" (Found C 76.4; H, 12.0. C18Ha02 requires C 76.6; H 12.1%). n-HexadeciyZmetone (Pdmitoykrcetone) .-n-Pentadecyl methy OBSERVATIONS ON !lTiE CLBISEN REACTION. 2895 ketone (5 g.) obtained from p h i t i c acid wa.~ condensed with ethyl acetate (7 mols.) by the general method the time of refluXing being raised to 5 hours. The copper salt (yield 2.2 g.; 34%) after purification melted at 112" (Found Cu 9.6.C38Hm04h requires Cu 9.7%). The decompoaifion of the copper salt by dilute sulphuric mid in presence of ether took an excessive time. Accordingly in this cam and in the case of all the higher members of the aeries the copper derivative was suspended in water an equal volume of concentrated acid added and the mixture allowed to cool before being extracted with ether. The free diketone cryshllised from alcohol in colourless plates, m. p. 49" (Found C 76.8; H 12.3. C19H3602 requires C 77.0; H 12.2%). n-Heptadeuqhetone (Margaroyhetone).-The condensation of the ketone (5 g.) obtained from margaric acid was carried out with 3 6 and 9 mob. of ester respectively the time of refluxing being 5 hours. The yields of copper salt were 0.35 g.1.7 g. (27%) and 1.4 g. and of recovered ketone 4.0 g. 2.5 g. and 2-9 g. respectively. In each case a small amount of copper margarate was produced. The copper salt of the diketone was washed with cold ether. The unchanged ketone was then separated from the copper margarate in the waahings by acidification treatment with barium acetate, and filtration of the insoluble barium salt. The pure copper salt melted at 112" (Found Cu 9.3. C,H,,O,CU requires Cu 9*3y0) and the free diketone at 51" (Found C 77.3 ; H 12.3. n-C&oyluc&tone (Stmroyhetone) .-In a repetition of previous work 10 g. of n-heptadecyl methyl ketone were condensed with ethyl acetate (35 mols.) and sodium and 0.75 g. of copper diketone waa obtained on ad- cupric acetate and alcohol to the reaction mixture (yield 6%).With 8 mols. of ester 6.9 g. of copper salt were obtained (yield 55%). No diketone copper salt was ever obtained until alcohol was added to the reaction mixture this accounting for some of the earlier negative results. The purified salt melted at 113" (Found Cu 9.0. C,,H,,O,Cu requires Cu, The free dikdone crystallised from alcohol in colourless plates, m. p. 52-5" and gave a red coloration with alcoholic ferric chloride on warming (Pound C 77.5; H 12.4. C,1Ha02 requires C, 77.8; H 12.35%). n-~70nabdecoylctcetone.-)~-Octadecyl methyl ketone wa8 obtained from the C acid by the general degradation process. Condensing with ethyl acetate gave a 320/ yield of a copper dikdone some C,H,,O requires C 77.4; H 12.3%). 9*OY0) 2896 HINSHELWOOD AND BURK : unchanged ketone being recovered.The pure salt orysfallised from benzene melted a t 112.5" (Found Cu 8.6. CMHWO4Cu requires Cu 8.6%). The recovered dikane consisted of thin plates m. p. 55" (Found : C 77.9; H 12.5. n-Eicosan~~etone.-Pot~ium erucate wits fused with caustic potash giving acetic acid and the normal C acid eicosanic acid. After purification this was converted into its barium salt which C22H4i02 requires C 78-1 ; H 12.4%). F I G . 1. 360 220 t 180 h 140 loot was then distilled with -barium acetate. The wnonadecyl methyl ketone obtained was condensed with ethyl acetate in the general manner to give the corresponding copper derivative 5 g. yielding 1-75 g. (28.4%). Crystallbed from benzene the salt melted at 114" (Found Cu 8-15. C4,H,,04Cu requires Cu 8.3%). The free diketone melted a t 57" (Found C 78.4; H 12.6. C&HMO2 requires C 7 8 4 ; H, In the diagram curve I shows a noteworthy change in the fusi-1 2 -5 yo ) * bility of copper p-diketones with lengthening of the carbon chain. Curves I1 and I11 indicate the boiling points of the lower diketones and the melt4ing points of the higher diketones respectively. The authors desire to thank the Advisory Council for Scientific and Industrial Research and the Birmingham University Research Committee for grants which have helped to defray the expense of this investigation. 0 4 S 12 16 20 n in CnH,+,.CO.CH,.CO.CH, UN~VERSITY OF BIRMINGHAM, EDGB-4STON. [Received il-ovember 4th 1925.

ISSN:0368-1645    

DOI:10.1039/CT9252702891

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年代:1925

数据来源: RSC

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2896 HINSHELWOOD AND BURK : CCCCI1.-The Relation of Homogeneous to Cutulysed The Catalytic Decomposition of Hydro- Reactions. gen Iodide on the Xurface of Platinum. By CYRIL NORMAN HINSHELWOOD and ROBERT EMMETT BURB. THE results of several previous investigations (this vol. pp. 327, 1105 1552; Proc. Rmj. Soc. 1925 A 108 211) havc rcndere probable the conclusion that simple gaseous decompositions wh.i~h as homogeneous reactions are bimolecular become llnimolecuh when they take place in contact with the surface of a solid catalyst. Thus for example the thermal decomposition of nitrous oxide, 2N,O = ZN2 + O, aa an uncatalysed reaction depends upon the collision of two molecules but the reaction which fakes place upon the surface of gold appears to be simply N,O = N + 0 followed by the combination of atomic oxygen fo the molecular form.The decompositions of nitrous oxide on the surface of platinum and of ammonia on the surface of platinum have ako been shown to be nnimoleculaz. It is not always possible to decide from measurements of reaction rate whether a catalytic reaction is unimolecular or bimoleculm. If the active surface of the catalyst is completely covered with adsorbed molecules-'saturated'-then the reaction rate is inde-pendent of the pressure of the gas. The reaction appears to be of 'zero order.' When on the other hand the adsorption is small, the chance of a group of n molecules occupying positions on the surface near enough for interaction to be possible is proportional to the nth power of the total number adsorbed and this in turn to the nth power of the pressure of the gas.The ' order ' of the reaction obtained from kinetic measurements gives under these conditions the number of molecules actually participating in the decomposition. An intermediate condition is possible when the adsorption is neither very large nor quite small where a birnole-cular reaction might simulate a unimolecular reaction over a small range of pressure. But if the reaction order appeared to be unity by a coincidence of this kind it would vary very markedly both with pressure and with temperature as may easily be seen. This state of affairs would readily be detected and the results discounted, so that in general we may say that unless the reaction order is zero it gives the number of molecules participating in the change.The decomposition of ammonia on tungsten and of hydrogen iodide on gold are both approximately of order zero; consequently we cannot conclude how many molecules are involved. The homogeneous decomposition of hydrogen iodide is one of the best known bimolecular reactions. We were anxious therefore to find a catalyst at the surface of which the true order of the hetero-geneous reaction could be found. Platinum fulfils these con-ditions. The reaction takes place in the simple unimolecular manner HI = H +I followed by the combination of atomic hydrogen and iodine to form molecules. This illustrates once more the f undameiital importance in hetero 2898 HINSHELWOOD AND B U X : geneow crtfalysis of the rtfEinity which metal surfaces possess for free atoms.Method of Ezperimnt.-The hydrogen iodide ww prepared by the action of phosphoric acid on potassium iodide and purified by fractional distillation from liquid air the middle fraction being collected in evacuated blackened glass holders. The decomposition was allowed to take place at the surface of a heated platinum wire and measured exactly 8.5 described for the corresponding experiments with a gold wire (this vol. p. 1552). The reaction vessel was kept in ice. Since the iodine condensed, the reaction 2HI = H + I is attended by a decrease in pressure which allows the rate to be measured by simple manometric means. That the action of the platinum wire was 'catalytic,' and that the wire w&s not attacked by the iodine was shown by the fact that the theoretical change in pressure was observed after complete decomposition and by the fact that the resistance of the wire remained absolutely unchanged during the whole series of experiments.Its catalytic activity moreover remained steady. The mercury in the manometer was protected from the action of the hydrogen iodide by a buffer of hydrogen in the capillary tube leading to the decomposition bulb. In$uence of the Pressure of the Hydrogen Iodi&.-Three typical experiments showing the course of the reaction a t different tem-peratures will first be recorded t is the time in seconds x the percentage change and k the unimolecular velocity coefficient. 670". 200 Mm. HI. 100 Mm. H,. 100 22 24.9 200 41 26.4 300 56 27-4 400 64 25.6 500 '72 25-5 600 76 24.0 t .x. k x 104. 563O. 200 Mm. HI. 100 Mm. H,. t. x. k x lo4. 120 12 10.6 300 27 10.3 600 47 10.6 900 61 10.5 1200 71 10.4 1600 78 10.1 439". 200 Mm. €€I. 100 Mm. H,. t . x. k x lo' 600 13 2-32 1200 26 2-50 1800 38 2.65 2400 46 2-49 3300 55 2.42 4200 63.5 2.40 6000 74.5 2.28 The influence of the pressure of the hydrogen iodide is shown 100 Mm. of hydrogen were by the following values found a t 563". present in each experiment. Press. of HI (mm.) ......... 100 200 300 k ................................. 0.001 18 0.00 105 0.00095 The values of k are sufficiently independent of pressure to ahow that the reaction is unimolecular. The slight dropping off was traced to the circumstance that hydrogen has a small but defmite retarding effect on the reaction.When the initial pressure o hydrogen iodide is great the pressure of hydrogen a t every stage of the reaction is greater than when the initial pressure of hydrogen iodide is small. The slight falling off in rate due to the adsorption of hydrogen by the wire is shown by the following table. 200 Mm. of hydrogen iodide were used in each experiment. Preai. of H (mm.) ......... 0 100 200 k (average) .................. 040126 040105 0.00092 The Influence of Temperature.-This is shown in the following The values of k are those corresponding to a hydrogen table. pressure of 100 mm. T (abe.) ........................ 943O 836O 712O k 0-00105 0400244 ................................. 0.00268 E (cals.) 13,700 13,850 ........................lKec7mni.m of the Reaction.-We suggest the simplest possible interpretation of the resulh namely that the reaction at the surface of the platinum is the simple change HI = H + I. The apparently unimolecular course could be explained in another way by assuming that there existed one complete layer of hydrogen iodide molecules on the surface of the catalyst and that reaction took place when a molecule from the gas phase struck one of the molecules in this layer. There are however several vital objec-tions to this. First there is abundant evidence to show that where two molecules interact in heterogeneous reactions they must in general both be actually adsorbed. This is shown by the fact that in reactions where A and B interact excess of either A or B can actually retard the reaction by displacing the other from the surface.Secondly if there is a complete layer there is no reamn why the molecules in it should not react among them-selves instead of waiting for impacts from the gas phase. Thirdly, if the heterogeneous reaction depended upon impacts from the gas phase the rate could never become independent of pressure as it does when it takes place at the surface of gold. Attention may be directed to one further point of interest which emerges from these experiments. The retarding effect of hydrogen on the reaction is but slight. When the catalytic decomposition of ammonia was investigated on the same wireand actually at a higher temperature-it was found to be retarded in a most pro-nounced manner by hydrogen. It cannot be argued that hydrogen iodide is too strongly adsorbed to be displaced by hydrogen whiM ammonia is easily displaceable because the come of a d o l e -cular reaction can be revealed only when the adsorption is small. Hence we must conclude once more that different reactions are provoked at different points (‘active centres ’) on the catalytic surface Summary. In continuation of a general investigation of the influence of catalytic surfaces on reactions which in the homogeneous gas phase are bimolecular it has been shown that the thermal decom-position of hydrogen iodide in contact with platinum is kinetically unimolecular. Reasons are given for believing that this proves the decomposition to take place in the simple manner HI = H + I. PHYSICAL CHEMISTRY LABORATORY, BALLIOL COLLEGE AND TRINITY COLLEGE, OXFORD. [Received November a h 1925.

ISSN:0368-1645    

DOI:10.1039/CT9252702896

出版商:RSC    

年代:1925

数据来源: RSC

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CCCCII1.-Oxidation of Ethyl Ether to Oxalic Acid in Presence of Uranyl Nitrate. By SYDNEY WILLLAM ROWELL and ALEXANDER SMITH RUSSELL. WHEN uratnyl nitrate dissolved in ether is exposed to sunlight in presence of water a yellow precipibte sometimes forms in the aqueous layer especially after the solution has been standing in tJhe light for some days; at other times a black slimy mass forms in the aqueous layer. These compounds are the subject of the present investigation. There is only one reference in the literature to the composition of the yellow compound (Soddy “Chemistry of the Radioelements,” 1911 p. 32). Soddy found that a yellow powder of empirical formula UCH40 remained after distilling the ether from an ethereal solution of uranyl nitrate. On decomposition, this compound formed a basic carbonate which lost carbon dioxide and water at 200-300”.E x P E R I M E N T A L . Preparation of the Yellow Compound.-In a typical experiment a mixture of 60 g. of ethyl ether 60 g. of uranyl nitrate and 20-60 g. of water after being shaken until the nitrate dissolved was exposed ta bright sunlight for periods up to 24 hours. The ether was then removed by distillation at as low a temperature as possible, and the aqueous solution evaporated. On cooling there separated a yellow compound mixed with uranyl nitrate which was freed from the latter by washing with cold water in which the former was comparatively insoluble. The yield was poor and rarely exceeded 12 g. The yellow compound was found to be identical in properties with the normal hydrated oxalate of uranium, U0,C,04,2&0 (Found U 60.5 ; C,O, 22.2 ; H,O 9-7 ; C 6.1 ; H 1.2.Calc. U 604; C,O, 22.3; H20 9.1 C 6.1 ; H l-Oy&) ETHER TO OXALIC ACID IN PRESENCE OF URANYL NITRATE. 2901 Uranium was determined gravimetrically as U,O, and oxdafe volumetrically . Formation of a New Basic Omlute of Uranium-In a few of the above experiments the compound which resulted appeared different -from the normal oxalate ; it had a lighter yellow colour. It gave the u d reactions of an oxalate (Found U 68-0; C,O, 1200%). The basic oxalates which comeqond with the normal oxalates would be U( OH),,U0,C20,,2~0 and UO,( OH),,U0,C,04,2~0, depending whether the uranium in the hydroxide is quradri- or sexa-valent. The former of these contains U 68.0; C204 12.6% and the latter U 68.2; C,O, 12.6%.Either of these might be the compound analysed above. Since the compound U(OH) is stabler than UO,(OH), we are inclined to prefer the first formula. It may be written UCH40, which is identical with that of Soddy’s product. The formula of the other product so h t t e n , differs however only by a single hydrogen atom. There is no doubt that a basic oxalate is formed by the interaction of uranyl nitrate and ether in the presence of sunlight and it is probable that Soddy’s product was this oxalate. Fopmation of Uranous Eydroxide.-We find that when uranyl nitrate in solution in ether is neutralised so that a precipitate is just not formed and exposed to sunlight for periods of a few hours, there settles from solution a black or greenish-black slimy preci-pitate which accompanies the basic and normal oxalates.. It is not formed in solutions of uranyl nitrate containing free nitric acid. It resembles the product obtained by adding ammonia to a solution of a uranous.salt namely U(OH), and this composition waa con-h e d by analysis (Found U 78.0. Calc. U 77.8%). These observations are in agreement with the work of Aloy and Rodier (Bull. Soc. chim. 1920 27 101; 1922 31 246) and of Aloy and Valdiguid (ibid. 1925 37 1135) who found that in neutral solution uranium salts on exposure to sunlight in the presence of certain organic compounds yield a black or a violet precipitate the former being manous hydroxide and the latter of composition U30,,2Q0, through partial reduction of the uranyl salt.It is evident from these results that the composition of these lower oxides like that of the oxalates varies with the conditions in which they are formed. Suggested Mechanism of the Reaction.-In the absence of sunlight, none of the products described above is formed. Exposure to sunlight is therefore essential to the reactions. The oxalates formed are not oxidation products of an impurity in the ether for the most carefully purified ether gave the oxalate and addition of alcohol the most likely impurity did not increase the yield. More-over no oxalate resulted when alcohol replaced ether in the solutio 2902 OXIDATION OF ETHPI; ETHER TO OXALIC ACID ETC. of uranyl nitrate although we found atii Aloy and his co-workers did that it favours the formation of a hydroxide of uranium in neutral solution.No oxalate was obtained when other uranyl salts replaced the nitrate. Ebelman (Ann. Chim. Phys. 1842,5,198) first pointed out that solutions of the uranyl salts of strong acids were changed by sunlight in presence of an oxidisable compound acquiring a green colour which we now know to be due to uranous salts and this work has been greatly extended by Aloy and co-workers (Zoc. cit.). On their view if A be an acceptor of oxygen e.g. alcohol and uranyl nitrate the salt considered the reaction proceeds in sunlight as U02(N0,) + 2HN0 + A = U(NO,) + H,O + A 0 in presence of a sufliciency of nitric acid. If suflicient acid be not present it is to be expected that some uranous hydroxide would be formed and this is what we have found.When ether is the acceptor it is oxidised finally we find to oxalic acid. In presence of uranyl ion and free nitric acid this would be expected to form the normal oxalate as it does; in presence of insufficient acid a mixture of the normal oxalate and uranous hydroxide or a compound of these would be expected to form. The manner of oxidation of ether to oxalic acid has not been previously considered in the literature. We suggest the following. Ether is oxidised to diglycol when the uranyl is reduced to the uranous ion by sunlight. Part of the diglycol is oxidised by nitric acid to diglycollic acid and part hydrolysed to glycol which is then further oxidised by nitric acid to oxalic acid thus : / diglycollic acid. ‘ s glycol + oxalic acid. We find the latter. Ether + diglycol It is of course known that diglycol is oxidised by nitric acid partly to oxalic acid but mostly to diglycollic acid. It has not yet been possible to test this scheme by showing the presence of either diglycol or diglycollic acid. A generous grant from the Caird Fund of the British Association DR. LEE’S LABORATORY, provided the materials of this research. CHRIST CHURCH OXFORD. [Received hlovemher 23rd 1925.

ISSN:0368-1645    

DOI:10.1039/CT9252702900

出版商:RSC    

年代:1925

数据来源: RSC

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POLYMEBXSATION OF ~43LUCOSAN. 2903 CCCC1V.-Polymerisation of i3-Glucosan. The Cons-titution of Synthetic Dextrins. By JAMES COLQUHOUN IRVINE and JOHN WALTER HYDE OLDEAM. ONE method of appzoach to the constitutional problems of the polysaccharides is through the study of anhydro-hexoses and the discovery by Pictet and his collaborators that p-glucosan can be p r e p d conveniently by the dry distillation of starch acquires a special importance in this connexion. 1 6-Anhydroglucose has in this way been rendered available in quantity and ifs properties have been examined in detail by Pictet and others. One of the most striking of the new observations is that the compound is readily polymerised the reaction n(C6H1005) + (C6H1,05) pro-ceeding readily when p-glucosan is heated either alone or in the presence of catalysts.Thus when fused with platinum black, glucosan is converted into an amorphous powder to which the formula (C6HI0O,) applies and this displays the general properties of a dextrin yielding glucose on hydrolysis (Pictet Edw. Chim. A& 1918 1 226). Pictet finding platinum black uncertain in its action improved the method by using zinc chloride as a catalyst (&bid. 1921 4 788) and he also varied the procedure by con-ducting the polymerisation under both reduced and increased pressure. Four definite compounds were obtained under these conditions : Polymeride. C.1,. PIWSW0. 1. Diglucomn ........................... + 28.2' 16 mm. 4. Octaglucosan ........................ + 72.8' 13-2 ,) 2. Tetraglucosan .....................+ 11 1.9' 1 atmos. 3. Hexaglucosan + 94.1' 4.6 1 ) ..................... Although there seems no theoretical limit to the number or variety of possible polymerides the above list includes only compounds in which glucosan molecules may be regarded as having become associated in multiples of two. The mode of affachment of the parent molecules has hitherto save in one case remained obscure, but Pictet has recorded the abnormality that the polymerides yield only diacetates or dibenzoates in place of the tri-derivatives to be expected. By arrangement with Professor Pictet we have been engaged on the constitutional study of the polyglucosans and take this opportunity of expressing our thanks for his courteous permission td extend his work. The completion of the investigation which was commenced four years ago has been delayed in consequence of the complexity of the results and in the meantime Pringshei dm IRVINE AND OLDHAM POLYME~USATION OF ~-GLUCOSAN.has described the application of the methylation process to tetra-glucosan (Ber. 1922 55 3001). No difficulty was apparently experienced by him in obtaining complete alkylation and on hydrolysis of the product both tetramethyl and dimethyl glucose were obtained. This is a striking result but a,s shown by Ring-sheim it is in itself insufficient to discriminate between two a,lternative structures for tetraglucosan. In order to obtain an adequate view of the mechanism of the polymerisation of glucosan it is necessary to study the constitution of a variety of polymerides displaying a progressive increase in molecular complexity and this we have accomplished.In repeat-ing Pictet's experiments little success was attained in using platinum black as a catalyst and after numerous attempts to find a superior reagent we adopted the method of heating glucosan a t 250" in the presence of zinc dust. The polymerisation was conducted in a vacuum the residual air having been washed out with hydrogen and under these conditions the change took place without charring or alteration in weight.* As the zinc dust employed contained a trace of chloride it is possible that the latter is the functional catalyst as we find that zinc chloride exercises a powerful poly-merising effect on glucosan and its derivatives the reaction in some instances being violent.For many reasons we prefer the use of metallic zinc and although polymerides differing from those described by Pictet are produced we have continued to employ the process as it proved satisfactory for large-scale working and gave uniform results. It may be remarked however that the relative yield of the different dextrins is affected not only by the catalyst but also by the temperature by the duration of heating, and by the scale of working. In order to obtain polymerides of high molecular weight it is unnecessary in our experience to work under positive pressures, and all our preparations were carried out a t 15 mm. By means of fractional precipitation from aqueous solution the polymerides were separated into three main fractions which in order of increas-ing solubility showed the following progressive diminution in * It may be mentioned that glucosan is much less stable at high tem-peratures particularly in the presence of acids than the method of preparing the compound would suggest.Nevertheless Venn ( J . Text. Id. 1924 15T, 414) having found that the yield of glucosan from cellulose is greatest when the acidity of the distillate is lowest states that this result is opposed to our views as to the origin of the hexosaa. It would have been surprising if any other result had been obtained and Venn's observation which amounts to no more than the statement that the best yields of glucosan are obtained under the most favourable experimental conditions has no bearing on the mechanism of tlie reactions in which gluoosan is fonnocl THE CONSTITUTION OF SYNTHETIC DEXTIUNS.2906 specific rotation. Dextrin I + 83-9"; Dextrin 11 + 60.7" ; Dex-trin 111 + 29.9". In marked distinction to the products described by Pictet all the dextrins yielded a definite triacetate and the presence of three hydroxyl groups per C unit was confirmed by methylation. The convenient solubilities of these trimethyl dexfrins rendered possible the determination of their molecular weights in benzene solution and in this way the parent compounds were characterid as containing respectively seven four and three glucosan units. Trimethyl Dextrin I 1446 1428 Heptaglucosen Methylated product. Mol. wt. (found). Mol. wt. (calc.). Parent compound. 9 ) 9 9 II 874 816 Tetraglucoean Y Y 3 9 III 595 612 Triglucosan This does not exhaust the list of polyglucosam as we have also obtained other isomerides and it is evident that both odd and even numbers of glucosan molecules are capable of forming poly-merides.Further it is clear that the tetraglucosan examined in the course of the present investigation is Merent from that described by Pictet and subsequently examined by Pringsheim. The distinction is shown in the specific rotations of the compounds, in the m. p. of the triacefates prepared from them and most emphatically in the different behaviour of their methylated deriv-atives on hydrolysis. The methylated dextrins which may now be termed hepta-, tetra- and tri- (trimethyl glucosan) respectively were examined so as to give an insight into the mode of attachment of the constituent hexose chains the information being derived by identifying the methylated glucoses formed on hydrolysing each compound.In order to indicate the significance of these results it may be recalled that although it is cwtomary to distribute the hydroxyl groups equally among the C units of a polysaccharide or allied compound, this allocation is based on an assumption and should be subjected to experimental test in each case. Thus cellulose and hexa-amylose (Irvine Pringsheim and Macdonald J. 1924 125 a) which are isomeric with the dextrins now under consideration give tri-methyl derivatives and these in turn yield on hydrolysis 2 3 6-tri-methyl glucose and no other sugar. It follows that the hydmxyl groups in the parent compounds are uniformly &tributed Le., each C unit carries three hydroxyh arranged in the same positions.Were this not the case isomeric trimethyl glucoses would be formed or alternatively a mixture of methylated sugars such as tetramethyl and dimethyl glucoses giving the same average composition. In marked contrast to natural polysaccharides the syntheti 2906 II(vME AND OLDEAM POLYMERISATION OF p-OLUCOSAJY. dextrins afford rstriking examples of compounds constituted on an entirely Merent model in that the hydroxyl groups are not attached uniformly to the individual C units. We have already shown (J. 1921 119 1744) that when P-glucosan is subjected to consecutive methylation and hydrolysis it gives 2 3 5-trimethyl glucose and on the basis of analogy it might reasonably be expected that the same end-product would be obtained from a polymerised glucosan.Such is not the case. Each trimethyl dextrin was converted into the corresponding methylated methylglucosides and thereaffer into the constituent sugars but the product in place of being homogeneous consisted in each case of di- tri- and tetra-methyl glucose mixed in proportions which gave the analytical mes required for a trimethyl glucose alone. The individual sugars were separated and two of them were characterised as 2 3 5 6-tetramethyl glucose and 2 3 $trimethyl glucose but the constitution of the dimethyl sugar is still uncertain and two alternatives are possible. Although in this section of our work we did not conduct the separation of the above sugars on quantita-tive lines good reasons exist for the belief that hepta- tetra- and tri-(trimethyl glucosan) all give the same methylated glucoses as the phyaical constants of each mixture were identical.It is necessary to emphasise that the tetramethyl glucose isolated in these experiments is a genuine scission product of the methylated dextrins and does not originate in any molecular cleavage during the methylation process. This possibility wits carefully excluded, and the result in itself disposes of the idea that the polymerisation of glucosan is merely the union of intact molecules in pairs. The process is evidently complex and consists essentially in the form-ation of glucosidoglucosides which show a general structural resemblance with the constitutional type.ascribed by Hess to cellulose. The development of structural formulae for the poly-glacosans demands however a knowledge of the relative propor-tions of the different methylated glucoses into which they can be transformed. A considerable advance was made by conducting all the operations from the polymerisation of the glucosan to the separation of the methylated glucoses finally obtained on strictly quantitative lines. For this purpose large quantities of material were required and a substantial simplification was effected by methylating the total polymerised product and separating the isomerides by vacuum distillation without isolation of the parent compounds. The first fraction consisted of monomeric trimethyl glucosan whilst the second was a viscous syrup which was shown to be di (trimethyl glucosan).The remaining syrup which con-stituted the largest fraction was practically non-volatile a t 2OO0/0. !CHE CONSTITDTION OF SYNTHETIC DEXTRZNS. 2907 mm. and on cooling it solidified to a clear red glass. As fhis product contained all polymerides higher than the dimeride it is termed poly (trimethyl glucosan). Di(trimethy1 glucosrtn) was converted into the methylglucosides of the constituent sugars the products being formed in the pro-portions shown below Yield %. Calc. for Found. equal mols. flDimethyl methylglucoside. 46-6 47.1 Di(trimethy1 glucosan) Tetramethyl methylglucoside. 53.4 52.9 These proportions were confirmed from the yields of the corre-sponding sugars when as before 2 3 5 6-tetramethyl glucose was isolated together with a dimethyl glucose.An equally sigdicant result was obtained by similar treatment of poly(trimethy1 glucosan) three glucosidic products being obtained in place of two. Yield %. Calc. for Found. equal mob. f 2 3 5 6-Tetramethyl 35-5 35-3 Poly(trimethy1 glucosan)+ 2 3 5-Trimethyl methyl- 33.5 33.3 ,/ methylglucoside. \ glucmide. \ Dimethyl methylglucoside. 26.0 Monomethyl methylglucoside. 5.0) 31'4 As shown by the analytical figures quoted in the experimental part the small amount of monomethyl methylglucoside is attribut -able to incomplete methylation and may be added to the yield of the higher homologue. Discussion is simplified by tabulating the significant facts show-ing the mutual relationships between glucosan and the polymerides now described.[LID of [alv of Mol. wt. of parent cp compound. trimethyl derivative. (water) (MeOH) p-Glucoaan ... -65.4" -53.2" 212 (204) Diglucosan ... - +48.3 418 (408) Triglucosan ... +29-9 +52% 595 (612) Tetraglucosan +60-7 f-68.7 873 (816) Heptaglucosan +85-8 +89.4 1446 (1428) Pol yglucosan - I -yo Yethoxyl content of derived Methylated sugars glucosides. produced. 50.9 51.2 - glucose 2 3 5-Trimethyl glucose. 2 3 5 &Tetramethyl 1. Dimethyl'glucose. ( 2 3 5 &Tetramethyl glUCOSe. 2 3 5-Trimethyl glucose. 49-7 i Dimethyl glucose. 49.6 S f 50-4 50.6 The hove teth- tri- and di-methyl glucosea in exactly molecular proportions. Including Pictet's results a series of polymerides from mono-fo octa-glucosan is now complete with the exception of the penta-form.It will be observed from the table that polymerisation alters the sign of rotation which increases in the dextro sense, with the molecular magnitude this possibility having been fore-VOL. CXXVII. 5 2908 IRVINE AND OLDHAM POLYMERISATION OF ~I-GLUCOSAN. seen through our studies of inulin and starch. The optical effect of methylation is also consistent with previous experience but the essential fact which emerges from the results given in the table is that mono- and di-glucosan are unique members of the series. The former gives rise to only one methylated sugar (2 3 5-tri-methyl glucose) and the latter yields a mixture from which trimethyl glucose is absent.Thereafter in the higher polymerides 2 ; 3 5-tri-methyl glucose is again encountered as an end-product and in the case of the mixed polyglucosans this sugar is present in equi-molecular proportion with the higher and lower homologues. This represents an average result to which all polymerides higher than diglucosan have contributed and the discussion can therefore be focussed on the three types represented by (a) mono- ( b ) di- and (c) ply-glucosan. Mechanism of the Polymerisation. The initial step of the polymerisation can be traced from the s-cant fact that 2 3 5 6-tetramethyl glucose and a dimethyl glucose are invariable products from all the polyglucosans. It follows that the fist action is the conversion of glucosan into glucose one molecule of which condenses with a second molecule of glucosan so that once the process is initiated it is catalytically continued.The experimental conditions employed in the poly-merisation are favourable to this cycle of reactions and no other explanation seems possible. If this be correct the dimeride should differ from the monomeric parent in having the hydroxyl groups unequally distributed in the ratio of four in one glucose residue to two in the other. The results obtained show that this con-sideration applies quantitatively. The precise way in which glucose condenses with a molecule of glucosan must nevertheless remain unknown until the constitution of the dimethyl glucose isolated from diglucosan has been established and despite laborious investigation this has not been solved.As shown in the experi-mental part however the sugar must be either 2 3- or 2 5-di-methyl glucose and as the latter alternative is more strongly supported it is provisionally adopted leading to the following structure for diglucosan : n 7c-, OH)*CH( OH)-CH*CH( OH)*CH,*OH B. Glucose residue. A. Gluco- &&due THE CONSTITU!FION OF SYNTHETIC DEXTRINS. 2909 Speculation on the next stage of the polymerisation is guided by the fact that all polymerides above diglucosan give 2 3 5-tri-methyl glucose. This can originate only from the molecular fragment B and not from A as otherwise the methylated sugars obtained from triglucosan would be two molecules of tetramethyl glucose and one molecule of monomethyl glucose. The attach-ment of the third glucose residue is thus desnitely restricted to position 6 of residue By giving the following constitution for tri-glucosan : r1 i 0 I rYH 6 YH-OH r -1 LC!H I YH-MH*CH( OH)*CH(OH)=CH*CH(OH)* H F 0 (IH~OH I As the yields of methylated sugars from tetra- and hepta-glucosan have no quantitative significance it is inaddable to discuss the further steps involved in the polymerisation but the examination of the mixed polyglucosans contributed valuable information.On occasions these higher glucosans formed as much as 75% of the total material polymerised so that they may be regarded as repre-sentative of the whole reaction. Inspection of the experimental details will show that this material not only gives the three methylated sugars required by the above formula but does so in precisely equimolecular proportions.This result has been verified on more than one occasion; it cannot be regarded as adventitious and it disposes of the possibility that the trimethyl glucose originates in a simple polymeride of glucosan in which the molecular con-stitution of the parent molecule is preserved. It is nevertheless, conceivable that molecules of monomeric glucosan may become associated either together or with simple polymerides and the existence of such compounds as hepta- and octa-glucosan indicates that this should not be ruled out. Further the tetraglucosan examined by Pringsheim yielded no trimethyl glucose but gave rise to the same sugars as we have now shown to originate from diglucosan. Taking a general survey of the results it is clear that the polymerisation involves reactions of two types one involving association and the other condensation.For example, when diglucosan is formed it may either condense with an addi-tional molecule of glucosan to give the trimeride which in turn, by further condensation yields a tetrameride or alternatively two dimeride molecules may become associated to give an entirely 5 ~ 2910 IRVINE AND OLDHAM POLYMERISATION OF ~-GLUCOSAN. different type of tetraglucosan. The inclusion of Pringsheim's results with our own renders this view more than speculative and a similar complexity may accompany each stage of the ply-merisation. Our results do not provide conclusive evidence on this point and reveal only the primary nature of the polymeris-at'ion.It is of special interest to note that two-thirds of the triglucosan formula consists of a residue present in the accepted formula for maltose a remarkable similarity in structure con-sidering the drastic conditions employed in the preparation of the trimeride. Triglucosan may in fact be regarded as qEucosan mdtoside. Further the P-configuration of the parent glucosan is preserved in the higher polymerides despite the pronounced changes in rotation which accompany their formation. The view now put forward demands that the condensation type of polymerisation is dependent on the presence of free hydroxyl groups and is supported by the fact that trimethyl glucosan was recovered unchanged when heated with zinc dust in an ex-hausted sealed tube at 250" for 10 hours.Under similar conditions the use of zinc chloride as a catalyst resulted in profound decom-position but on limiting the reaction to 3 hours at lW" the rotation altered from laevo to dextro owing to conversion of the glucosan into trimethyl glucosidotrimethyl glucose. Apnlicdility of the Methybtion Process to the Structural Problewis of Carbohydrates. The criticism has been put forward that our method of deter-mining the structure of carbohydrates although diagnostic in the case of simple sugars may not be applicable to the '' closed-chain structures " represented by polysaccharides and similar compounds. It is dif6cult in view of the mass of consistent results obtained with many types of non-reducing carbohydrates to find any justification for this objection; but as at present much reliance is placed on the validity of the methylation process as a means of determining constitution the occasion is opportune to take into account the essential requirements of the method.The principles developed in this laboratory can be applied to the structural problems of carbohydrates provided the following primary conditions are satisfied (1) that methylation does not alter the configuration of a sugar; (2) that methylation does not disturb the positions in which sugar residues are attached to each other or to other groups; and (3) that under the conditions employed in methylation and in hydrolysis non-glucosidic met hoxyl groups do not migrate from one position to another in a sugar chain. In default of direct experimental evidence to the coiitrary THE CONSTITUTION OF SYNTHETIC! DEXTRTNS.291 1 and in view of the following observations it may be claimed that the above requirements are satisfied. According to circumstances, the methylation of carbohydrates as practised by us is effected either by the silver oxide reaction or by the methyl sulphate method, used independently or in succession. It has been adequately proved that these alternative methods when applied to the =me compounds give the same methylated sugars the only distinction being that the alkaline reagent acts upon reducing sugars to @ve a larger excess of the corresponding p-glucoside. Configuration is therefore affected but only so far as the reducing group is con-cerned. The one aspect of conQuration however which is utilised in our deductions is that of the non-reducing groups and it h a long been known that the silver oxide reaction yields derivatives which retain the confirmration of the parent compound.The conversion of d-dimethoxysuccinic acid into d-tartaric acid (Purdie and Barbour J. 1901 79 972) is a convincing but by no means unique example of this regularity. In addition mono- di- tri-, and tetra-methyl glucose all of which were prepared by the silver oxide reaction have been demethylated and converted into glucose phenylosazone showing the correct optical activity. That the second and third requirements of the method are fulfilled is shown in numerous ways. For example Haworth and Leitch subjected maltose and cellobiose to identically the same methylating treatment yet isolated isomeric trimethyl glucoses in the two investigations.This result cannot be reconciled with the idea that molecular linkages are-altered by methylation or that the methyl groups fail to retain their positions. The evidence is equally clear in the case of the more unstable types of carbohydrate deriv-atives such as y-glucosides and the existence of isomeric tetramethyl glucoses and of the corresponding tetramethyl fructoses which reflect accurately the essential properties of the compounds from which they are derived may be quoted in illustration. In this connexion it is important to note that with the exception of the glucosidic alkyl group (which in any case is not concerned with our structural studies) the stability towards acids and alkalis of the methyl groups in a sugar chain is remarkable.Concentrated sodium hydroxide at the boiling point has no effect on a fully methylated hexose and in our experience the elimination of the methyl groups from an alk-ylated reducing sugar has been accom-plished only by such processes as boiling with concentrated hydriodic acid heating under pressure with glacial acetic acid saturated with hydrogen bromide or in one example,* by prolonged action with * This result which is unpublished was obtained with a dimethyl galactose which yielded a monomethyl galactosazone. A similar irregularity is reporte 2912 IRVINE AND OLDHAM POLYMERISATION OF ~-GLUCOSAN. the phenylosazone reagents. This stability is far removed from that encountered in cases where methyl groups have been shown to migrate or to enter an irregular position (see Kubota and Perkin, this vol.p. 1889). It is possible that the frequency with which 2 3 6-trimethyl glucose has been obtained from different polysaccharides may have suggested the idea that the reagents had converted definitely isomeric compounds into a common form so that the same sugar would inevitably be produced in all cases. The results of the present investigation go far to refute this remote possibility. The only practical distinction between the alkylation of a polysaccharide and that of a simple sugar is that; owing to solubility diflticulties and to steric hindrance it is necessary in the former case to use the methyl sulphate method throughout and to repeat the rnethyl-ation many times.This treatment may conceivably affect the degree of polymerisation of a compound but as the discussion does not involve this point it may be focussed on the question if the repeated use of the alkaline reagent gives results divergent from those obtained by restricted treatment with silver oxide and methyl iodide. For this purpose we have selected p-glucosan as a test substance and after ten methylations by means of methyl sulphate obtained a normal yield of the same crystalline trimethyl glucosan formerly prepared by the alternative method (Irvine and Oldham Zoc. cit.). On extending the process until a total of twenty treatments had been given the same product was again obtained. The result shows that even when the methyl sulphate process is repeated as often as in the case of cellulose starch and glycogen, the methyl groups enter the same positions in glucosan as they do when the silver oxide reaction is used only once and further, by Freudenberg and Hixon (Ber.1923 56 2119) and confhned by Levene and Meyer (J. BioZ. Chem. 1924 59 i 145) who found that a mono-methyl mannosediacetone was completely hydrolysed by treatment with very dilute acid a property which indicates that the compound waa a y-methyl-mannoside dimetone. Should this prove to be the case rearrangement may have taken place between a methyl group and an hopropylidene group during either methylation or hydrolysis. Numerous examples are now known of the reversible displacement of bopropylidene and methyl but the reaction proceeds in acid solution whereas Freudenberg’s process does not admit of this condition.Apparently the configuration of mannose is conducive to irregular results. It may be recalled (Irvine and Paterson J. 1914 105, 9 15) that one hydroxyl group in mannitol resists methylation completely and that when methylglucosamine (a-amino-methylmannoside) is acted upon by dilute nitrous acid not only is the amino-group removed but the methyl group which is otherwise remarkably stable also is eliminated. In con-sequence the aIkylated mannoses have not been applied by us to structural studies THE CONSTITUTION OF SYNTHETIC DEX'I"S. am 3 that aIkyl groups show no tendency to migrate to the 2 3 6 - p i -tions. The dextrins described in the present paper were 'also subjected to repeated methylation yet the sugar finally obtained consisted exclusively of 2 3 5-trimethyl glucose and no trace of the 2 3 6-isomeride was detected.Precisely the converse applies when cellulose is subjected to parallel treatment as 2 3 6-tri-methyl glucose alone constitutes the final product. It is difficult to imagine that these sharply differentiated results obtained under duplicate conditions are due to the vagaries of the reagents rather than to inherent structural differences in the parent compounds. Clearly however the silver oxide reaction when applied to polymerides tends to lower the degree of polymerisation zt8 indi-cated by a change in solubility and an alteration of the rotatory power in the direction of that of the parent unit.This phenomenon has already been encountered in the investigation of methylated inulin and has again been observed when for comparative purposes, the mixture of higher polyglucosans was subjected to this reaction. E x P E R I M E N T AL. Polymerisation of p-Glucosan.-AS the polymerisation of @-glucosan gives rise to a variety of komerides it is necessary to specify accurately the experimental method adopted in preparing the polymerides now described. In the h t series of preparations, small quantities (7 g.) of glucosan were used in each experiment and this weight of material together with 0.1 g. of zinc dmt was intro-duced into a 300 C.C. distilling flask the neck of which was sealed by a cork carrying a manometer. To the side limb a T-tube ww attached provided on one branch with a tap (A) leading to the water pump and on the other with two taps (B and C).These were placed closely together so that the enclosed volume was small, C being connected to a supply of pure dry hydrogen. The flask, which with the exception of the side fittings was immersed in an rtsbestos air-bath provided with windows was exhausted and the residual air washed out with hydrogen. After again evacuating the temperature of the bath was raised to 250" the tap A being closed when the glucosan began to melt M otherwise the compound volatilised unchanged. After about 15 minutes the melt became viscous and as frothing ensued the tap A was opened at intervals. In approximately 30 minutes from the start of the reaction the frothing usually became most severe and it was then necessary to close A and C and open B momentarily.A bubble of hydrogen was thus introduced which served to break the film of glucosan and thereafter both C and A were rapidly opened and closed. In from 60 to 75iminutes from the time the glucosan wa8 thoroughly melted 2914 IRVINE AND OLDHAM POLYMERISATION OF ~-GLUCOSAN. frothing became sluggish and unless A remained open for a con-siderable time ceased entirely. At this stage heating was stopped and the flask allowed to cool the vacuum being maintained. No loss of weight was recorded under the above conditions and no charring took place. Direct Isolation of Polyglucosans. The product of several preparations was extracted with the minimum quantity of hot water and on the addition of rectified spirit to the united solutions a dark-coloured precipitate was formed.This was removed and absolute alcohol added to the filtrate. The dextrin then separated as a fine powder except in casa where too much water was present when a sticky precipitate was produced. In such an event the liquid was decanted the residue dissolved in a small quantity of warm water and after removal of the solvent dried a t 100"/15 mm.; the product could then be readily powdered. The less-soluble dextrin obtained as above is referred to as " Dextrin I." The mother-Iiquor which had deposited Dextrin I was concentrated and the addition of alcohol repeated until no further precipitate was formed. In this way the material was separated into two further portions (Dextrins I1 and III) each fraction being relegated to its class on the basis of sol-ubility and specific rotation.Heptuglwsan.-The material was redissolved in hot water and boiled with charcoal a treatment which removed colouring matter and also diminished the yield considerably. Finally the compound was precipitated with alcohol and dried in a vacuum. Dextrin I was thus obtained as a slightly hygroscopic powder which although perfectly white gave a pale yellow solution in water. Analysis of different preparations gave C 44.5 44.45; H 6.4 6-2; ash 0.266 (C6H1,,05 requires C 44.4; H 6.2%). Dextrin I is insoluble in organic solvents with the exception of acetic acid but is freely soluble in water giving a non-reducing dextrorotatory solution. This value was obtained in different preparations and when a specimen of the material was fractionally precipitated with alcohol the most active fraction showed [.ID + 85.8" thus indicating the uniformity of the compound.Despite this observation and the fact that dextrin I was afterwards shown to be heptaglucosan the application of Karrer's method of determining the molecular magnitude of polymerised units by analysis of the sodium hydroxide compounds gave inconclusive results which lay between those required for For analytical and reference purposes the triucetak was prepared Emmination of Dextrin I . [.ID + 83.9" for c = 2-08. (c6H1005)3 and (c6H1005)4 THE CONSTITUTION OF SYNTHETIC DEX!L"S. 2915 by boding the dextrin until dissolved with excess of acetic anhydride containing zinc chloride.The product wm isolated by precipitation with water washing with ether and solution in a large excess of hot aholute alcohol from which it separated as a fine white powder. After three such treatments the m. p. was constant (142") (Found : C 49.95; H 5.6; CH3-C0,H 65.6. C,,H,,O requires C 50.0; H 5-55; CH,-CO,H 62.5%). The triacetate is insoluble in water, cold a.bsolute alcohol or ether soluble in other organic solvents including aqueous alcohol [.ID in 50% alcohol + 85-1" for c = 2.2315. When heated for 2 hours at 70" in methyl alcohol which was nearly saturated with hydrogen chloride the dextrin was com-pletely converted into methylglucoside. Initially excess of B-methylglucoside was formed but on continuing the reaction for 24 hours the equilibrium mixture was obtained from which pure a-methylglucoside was isolated in the usual manner (m.p. 164"; OMe 15.1%; [.ID in water + 158.4"). Tetraglucosan.-This substance was produced in greatest yield when the polymerisation of p-glucosan was carried out in quantities of 20 g. at a time a 600 C.C. flask being employed. The subsequent procedure was as described and after removal of dextrin I the more soluble products were fractionally precipitated with alcohol. Fractions showing similar rotatory power were mixed and again precipitated so that by prolonged repetition of this process the total product was ultimately separated into two portions which could not be further sub-divided. These showed respectively [a], + 60-7" and + 29.9" in aqueous solution and are indexed it5 dextrin II and dextrin 111.Both substances were h e white hygroscopic powders and had the same com-position as the parent glucosan. Dextrin 11 when acetylated as already described gave the same triacetate as dextrin I (Found: C 50.2; H 5.6; CH3*C0,H 63.6%). The specific rotation and melting point also agreed within experimental error and on hydrolysing the acetate with sodium hydroxide dextrin I was regenerated (Found C 44.5; H 6.1 ; [.ID + 81-5" for c = 2-14 in water. Dextrin I requires C 44.4 ; H 6.2% ; [.ID + 83.9" for The solid was covered with methyl alcohol and hydrogen chloride passed in from time to time until the dextrin dissolved after which the solution was diluted with more alcohol and heated at 70", polarimetric readings being taken every 15 minutes.In one hour the constant value [.ID + 94.5" (calc. on the weight of glucoside formed) was reached and the product was then isolated as usual. Examination of Dextrin I I . c = 2.08). Dextrin I1 was readily converted into methylglucoside. 5 F 3916 EWE AXD OLDHAM POLYMERISATION OF p-a~ucosm. A crystalline mixture of a- and p-methylglucosides was thus obtained from which the pure a-form was separated by crystallisation from alcohol (Found m. p. 165-166"; [.ID + 157.2"; OMe 15.6. a-Methylglucoside requires m. p. 165-166"; [.ID + 157.5"; OMe, 15.9%). When the above reaction was conducted a t No in place of 70° and was arrested after 45 minutes (3-methylglucoside was the chief product and the a-form was present only to the extent Triglucosan.-In all respects save aolubility and specific rotation dextrin I11 resembled dextrin 11.Like the latter it yielded apparently the same triacetate as dextrin I (Found C 50.1; H 5.6; CH,-CO,H 62.3%). The specific rotation in aqueous alcohol was however + 74.2" in place of 78.9", but this discrepancy appears to be due to a trace of impurity as, on treatment with sodium hydroxide dextrin I was regenerated. Dextrin I11 was also converted into methylglucoside in the usual way. The total crystalline product isolated showed [.ID + 92-9" for c = 1 in methyl alcohol and gave OMe 15.3%. On crystallis-ation from absolute alcohol pure a-methylglucoside displaying the standard constants was obtained. In this case also when the reaction wm restricted to heating a t 50" for 1 hour p-methyl-glucoside was the chief product.of 20%. Examination of Dextrin I I I . Methylation of the Individual Dextrins. As the methods adopted for the methylations have been described in previous papers from this laboratory only s i e c a n t results are now quoted: Heptag1ucosan.-The action of silver oxide and methyl iodide on a methyl-alcoholic solution was definitely arrested at the stage where two alkyl groups had been introduced per C unit. Product a colourless glass emily powdered. [.ID in chloroform + 76.0" for c = 0.6035 (Found C 50-65; H 7.4; OMe 32.4. C,H1,O requires C 50-5; H 7.4; OMe 32.6%). The methyl sulphate reaction was more effective repeated treatment with the reagents under conditions similar to those employed with inulin giving a product readily soluble in organic solvents and showing [aID in chloroform + 89.4" for c = 2.745.The methylation was however still incomplete but approximated to the trimethyl stage [Found C 53.0; H 7.5; OMe 40-9. (C9H1605),. requires C 52.9; H 7.8; OMe 45.5%]. No further purification was possi-ble as the compound which was isolated as a glass readily con-vertible into a white powder was exceedingly soluble in organic solvents with the exception of light petroleum. The molecular Methylation of Dextrin I THE CONS-ON OF SYNTHETIC DEX!L"S. 2917 weight determined in benzene by the crymopic method was 1446, whereas a hepta (trimethyl glucosan) C ~ O require;s 1428. As contrary to expectation methyl alcohol containing 1% of hydrogen chloride proved to be without action on the compound, simultaneous hydrolysis and condensation was effected by heating for 15 hours a t 70" with alcohol nearly saturated with the gas.No charring resulted from this drastic treatment and the specifx rotation showed the usual characteristic rise and fall during the change. ([.ID + 75-0"-+ 93-7" -+ 87.5"). The mixed glucosides were isolated by vacuum distillation as a colourless 'syrup (OMe 50.4%) and were hydrolysed therea,fter by means of 3% aqueous hydro-chloric acid to give a solution of methylated glucoses showing [.ID + 68.4". A syrup was finally obtained on distillation showing OMe 38.6% and yielding crystalline tetramethyl glucose on extrac-tion with boiling light petroleum. The rema.ining sugars were di-and tri-methyl glucoses in llnknown proportions.Tetraglucosan.-As a result of three methylations by the methyl sulphate method 18 g. of the dextrin were converted into 16-5 g. of a viscid syrup showing [.ID + 66.6" for c = 3.3335 in chloroform and having OMe 39.5%. Two further methylations raised the methoxyl content to 41.6% and four subsequent treatmenfg gave the maximum value of 43.4%. The product was a glass possessing the customary solubilities [Found C 53.0; H 7.8; OMe 43.4. (C9HI6OJn requires C, 52-9 ; H 7-8 ; OMe 45.5%]. Methylution of Dextrin I I . Solvent. C. [QIrD. Methyl alcohol ..................... 1-3625 + 68.7' Acetone .............................. 1.968 70.5 Chloroform ........................ 2.900 61.2 Molecular weight determined by the cryoscopic method in benzene solution = 873.Tetra (trimethyl glucosan) C,,H,O,, requires 816. When converted into the corresponding methylglucosides as described in the case of the hepta-isomeride the product on dis-tillation showed in successive experiments OMe 49-6 49.7% and [a],,+ 100.9" in water for c = 1.3016. On hydrolysis.with 4% aqueous hydrochloric acid the permanent value for the specific rotation was + 66-7". The mixture of sugars thus obtained had OMe 38.9% and was separated into (a) a fraction soluble in ether, amounting to about two-thirds of the total and (b) a fraction, consisting of the remainder soluble in acetone but not in ether. From the soluble portion tetramethyl glucose c r y s t a w spon-taneously and was identsed by analysis and by determination of the physical constants.The uncrystallisable sugars were mixed, 6F* 2918 IRVINE AND OLDHAM POLYMERISATION OF ,B-GLUCOSAN. converted into their methylglucosides distilled in three fractions, and analysed. The methoxyl contents in order of increasing volatility were respectively 38.3 44-8 and 53-4y0 showing that the compounds were derived from a di- and a tri-methyl glucose. In no case did any of the sugars give a phenylosazone and the incom-pletely methylated forms were convertible into the stable variety of tetramethyl glucose in 80% yields. It was necessary to emure that the tetramethyl glucose bolated did not originate in degradation during the methylation of the original dextrin. The methylated dextrin was therefore extracted repeatedly with boiling light petroleum but this did not cause any alteration in the methoxyl content.Further when heated at 200°/0.2 mm. the methylated dextrin distilled very slowly but analysis of the distillate showed that no tetramethyl methylglucoside was present. Trig1ucosan.-Twenty grams sub-jected to eleven successive treatments by the methyl sulphate reaction gave 15.3 g. of a colourless glass convertible into a white solid [Found C 52-7; H 7-8; OMe 42.2. (C,H,,O,) requires C 52.9; H 7.8; OMe 45-5y0]. Methylutwn of Dextrin I I I . Solvent. C. [a],. Chloroform ........................ 2.1035 + 53.5" Acetone .............................. 2-048 56-4 Methyl alcohol ..................... 1.753 62.8 The molecular weight determined by the cryoscopic method in benzene was 595.Tri(trimethy1 glucosan) C2,H48015 requires 612. When heated in a vacuum approximately one-half of the material distilled at 180-200"/0~5 mm. but this result was evidently due to depolymerisation as the distillate was a comparatively mobile syrup having nD = 1.4770 and [.ID in chloroform + 23.9". The composition remained unaltered (OMe 44.7 %) The methylated dextrin when subjected to the joint action of methyl alcohol and hydrogen chloride mas converted into the corresponding mixture of akylated methylglucosides the whole of the product being distill-able although over a wide temperature range. No fractionation was attempted the total distillate being hydrolysed in one experiment by b o w with 4% aqueous hydrochloric acid.It is sigm6cant that when hydrolysis was complete the corrected specific rotation of the solution was + 6 5 ~ 3 " ~ showing that the end products were the same its those obtained from the hepta- and tetra-isomerides. As before the sugars thus obtained were divided into ( a ) a fraction soluble in ether which yielded crystalline tetramethyl glucose and a trimethyl glucose and (b) a fraction soluble in acetone but not in ether. The less soluble sugar which was purified by dissolvin THE CONSTITUTTON OF SYNTHETIC DESTRTF-S. 2919 in chloroform and precipitating with ether possessed the com-position of a dimethyl glucose (Olvze 33-4%) but could not be obtained in a crystalline form and failed to give a phenylosazone. Both the di- and the tri-methyl glucose formed above belonged to the butylene-oxide series and polarimetric tests for the presence of 7-forms gave negative results.Indirect Isohtion of Polyglucosans in the Form of the Methylated Derivatives. In place of separating the polyglucosam by precipitation and conducting the methylations in Merelit experiments an alternative is to alkylate the total polymerised material and thereafter to separate the methylated products. The latter method proved to be more effective more economical and more decisive. Thirty grams of glucosan were polymerised as described in each experiment. By extraction of the product with boiling rectified spirit it was possible to remove unchanged glucosan together with the bulk of the dextrins of low molecular weight leaving polymerides of high molecular weight undissolved and in this way it was shown that both types of dextrin yielded normal triacetates.It was, however preferable to methylate the total product directly the methyl sulphate method being used throughout. A comparatively mobile syrup was thus obtained in good yield 80 g. of glucosan giving 73 g. of methylated polymeride. On distillation at the Gaede pump the product was separable as under : Fraction I. B. p. 135"/0-2 mm. 28 grams. Trimethyl glucosan. Fraction 11. B. p. 205-210"/0-2 mm. 17.1 grams. Di(trimethy1 glucosan). Residue. 27.2 grams. Poly(trimethy1 g l u c m ) . In a second preparation where more complete polymerisation was effected and where over-heating during distillation was avoided 60 g. of glucosan yielded 55 g.of methylated product which in turn gave : Trimethyl glucosan .................. 9.41 grams 17% Pol y (trime t hyl glucosan ) ......... 3 1 . 7 7 57.8% The monomeric trimethyl glucosan crystallised in the receiver ; the dimeride was a pale yellow clear viscous syrup (nD 1-4720) whilst the undistillable isomerides consisted of a glass. Di(trimethyZ gZucosan) .-The composition and physical constants of the distilled syrup showed very little variation in successive preparations [Found C 53-0 52-9; H 7-7 7.9; OMe 44.5; N cryoscopic in benzene 418. (C9H,,0,) requires C 52.9; H, 7.8; OMe 45.6%; M 4081. Di(trimethy1 glucosan) ............ 12.98 , 234% Solvent. C. [ . Chlorof o m ........................ 1-95 16 + 46.5" Methyl alcohol .....................1.8790 48.3 Acetone .............................. 2.0040 51. 2920 IRVINE AND OLDHAM POLYMERISATION OF ~-GLUCOSAN. Conversion into methyluted methy,?g~ucosides. This reaction was accomplished by boiling with methyl alcohol nearly saturated with hydrogen chloride the specific rotation corrected for the change of concentration becoming constant a t + 110.0". The mixed gluco-sides were isolated by distillation and although the liquid boiled over a wide range of temperature the product w~ts collected as a single fraction (yield 97% ; n 1.4587). Under these conditions the distillate should have the same composition as trimethyl methyl-glucoside and this was the case (Found C 50.8; H 8.5; OMe, 51-2. CloH,,06 requires C 50.8; H 8-5; OMe 52.5%). Separ-ation of the constituents was effected by dissolving in water con-taining sodium bicarbonate and extracting repeatedly with chloro-form.This treatment removed all glucosides containing four or more methoxyl groups per C unit lower methylated compounds remaining in the aqueous layer. The process can be applied quantitatively and as in the present case yields are of special importance the results of one exact experiment are quoted. 8.5483 Grams of di(trimethy1 glucosan) gave 4.9161 g. of methylated glucosides extractable with chloroform and 3.5824 g. were retained in the aqueous layer. The less soluble compound when isolated, Ciissolved in ether dried and recovered proved to be dimethyl methylglucoside showing [.ID + 108.4" in methyl alcohol and nD 1.4743 (Found C 48-7; H 8.2; OMe 41.2.Calc. for C,H1,06, C 48-8; H 8.1 ; OMe 4143%). Analysis of the syrup extracted with chloroform having shown that it consisted essentially of tetramethyl methylglucoside together with a little trimethyl methylglucoside the mixture was hydrolysed to give the corresponding sugars. On repeating the extraction with chloroform only tetramethyl glucose passed into the lower layer, whilst trimethyl glucose was retained in the aqueous layer. The tetramethyl glucose when recovered p d e d by distillation and recrystallised as usual displayed the correct melting point and rot-ation (Found C 50.8; H 8-4; OMe 52-0. Calc. for C1&2006, C 50.8; H 8.5; OMe 52.5%). In this way 3.2457 g. of pure sugar were obtained from 4.4717 g. of the mixed glucosides.The small amount of trimethyl glucose isolated shows that this sugar cannot be regarded as a definite molecular product but originates in unpolymerised trimethyl glucosan. Neglecting this by-product and small undistilled residues the relative yields of the hydrolysis sugars calculated as the correspondmg glucosides become : Calc. for equal Dimethyl methylglucoside . . . . . . . . . . . . . . . . . . 47.1% Tetramethyl methylglucoside ...... ......... 53.4 S2.9y0 Found. molecules. 46. THE CONSTITUTION OF SYNTHETIC DEXTIUENS. 292 1 Examination of Methyluted Polyglucosans.-The non-volatile residue left when di(trimethy1 glucosan) was separated by dis-tillation constituted the main product of the methylation of p l y -merised glucosan. After solution in ether filtration and removal of the solvent the mixture of higher polymerides was obtained as a clear glass.The carbon content was low although the composition was uniform in different preparations [Found C 52.4 52.4; H, 7.6 7.8; OMe 44.4 45.2. (C,H,,O,X requires C 52.9; H 7.8; OMe 45.5y0]. As from its method of preparation the material consisted of all polymerides higher than the dimeride no molecular weights were determined. Solvent. C. Calw Chloroform ........................ 1-850 + 63.3" Acetone .............................. 2.266 66.6 Methyl alcohol ..................... 1.765 64.4 Conversion by the action of acid methyl alcoho€ into the mixture of methylated glucosides gave a 95% yield of a colourless syrup, which was distilled under 0.4 mm. and collected in one portion with-out fractionation.The average composition of the total distilla,te should be the same as that of trimethyl methylglucoside but although this held approximately all the values were low (Found C 50.4; H 8.3; OMe 50.6. Calc. for C,,H,O, C 50.9; H 8.5; OMe, 52.5%). On separating the constituent glucosides by extraction of an aqueous solution containing sodium bicarbonate with chloroform, the syrup recovered from the extract weighed 69% of the original total and the remaining 31% was recovered from the water. The former was hydrolysed with 8% hydrochloric acid to give the corresponding methylated glucoses which were isolated in 94% yield. Analysis of the distilled sugars showed that tri- and tetra-methyl glucose were present in equimolecular proportions (Found : C 49.9 ; H 8.2 ; OMe 46.8.Calc. C 49.8 ; H 8.3 ; OMe 4703%). Separation of the sugars mas effected by the method of chloroform extraction 11-176 g. of the mixture giving 5.300 g. of crystdline tetramethyl glucose displaying the correct analytical figures and constants. The less soluble sugar was recovered from the water, distilled as a viscid syrup and identified as a trimethyl glucose (Found C 48.6; H 7.95; OMe 41.4. Calc. for C,H,,O, C, 48.6; H 8-1 ; OMe 41-8y0). The specific rotation in chloroform solution was + 72.5" but in order to identify it completely the sugar was converted successively into the diacetate the mono-acetobromo-derivative and finally into the corresponding trimethyl p-methylglucoside. These steps were controlled by blank experi-ments in which authentic 2 3 5-trimethyl glucose was used and the optical changes were parallel throughout.On nucleation wit 2922 IRVME AND OLDHAM POLYMERISATION OF ~-GLUCOSAN. 2 3 5-trimethyl P-methylglucoside the product crystallised and was purified as usual from light petroleum. The m. p. refractive index and specific rotation in methyl alcohol were correct (Found : C 50-7; H 8.5; OMe 51.9. Calc. for C10H20067 C 50.8; H 8.5; OMe 52.5%). The combined results show that the sugars extract-able by chloroform from aqueous solution are 2 3 5 6-tetra-methyl glucose and 2 3 5-trimethyl glucose in equimolecular proportion. The lower methylated glucoside retained in aqueous solution after extraction of the tetra- and tri-methyl methylglucosides with chloroform consisted of a viscid syrup (nD 1-4779 [a]= in methyl alcohol + 106.2").Although with material of this nature vacuum distillation is difficult this purification was undertaken to obtain more accurate analytical figures. Pure dimethyl methylglucoside was thus obtained as the main fraction (b. p. over 190"/0.4 mm.; nD 1.4743) (Found C 48.55; H 8.2; ONe 40.8. Dimethyl methylglucoside C9HI8O6 requires C 48.6 ; H 8.1 ; OMe 41.8%). The undistillable residue was a glass and consisted essentially of monomethyl methylglucoside (Found C 45.7 ; H 7-2 ; OMe 28.9. Calc. for C.&606 C 46.15; H 7.7; OMe 294%). About 5% of the total sugars formed from the dextrin consisted of this material which almost certainly originates in incomplete methylation. Attempts to establish the constitution of the dimethyl glucose isolated in the present section of the research led to no h a 1 conclu-sions. The sugar failed to crystallise and formed no phenylosazone ; it also failed to enter into condensation with acetone when dissolved in this reagent containing 0.2% of hydrogen chloride but reacted when the concentration of acid was raised to 1.3%. No definite benzylidene derivative could be prepared either from the sugar or from its methylglucoside but the combined results although not conclusive favour the view that of the two alternatives 2 3- or 2 5-dimethyl glucose the latter is more probable. We desire to express our indebtedness to the Department of Scientific and Industrial Research for a Research Assistantship granted to one of us. UNITED COLLEGE OF ST. SALVATOR AND ST. LEONARD, UNIVERSITY OF ST. ANDREWS. [Received October 16th 1925.

ISSN:0368-1645    

DOI:10.1039/CT9252702903

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

ETdECTRICAT~ CONDUCTIVITIES OF HYDROGEN CHLORIDE ETC. 8923 CCCCV.-The Electrical Conductivities of Hydrogen Chloride and Potassium Chloride in Water and Acetone- Water Mixtures. By THOMAS KERFOOT BROWSON and FRANK MAURICE CRAY. THE electrical conductivities of a large number of salts in acetone-water mixtures have been measured especially by Jones and his co-workers (Jones Bingham and McMaster 2. physikd. Chew ., 1906 57 193,257 ; Jones and Mahin Carnegie Institute of Wmhiszg-ton Publication 1913,180 193). The present investigation of the electrical conductivities of hydrogen chloride and potassium chloride in water and acetone-water mixtures was carried out to obtain information in connexion with a research upon the preparation of solutions of standard, hydrogen-ion concentration and the measurement of indicator ranges in an acetone-water mixture containing 10% by volume of wafer (Cray and Westrip Trans.F a r A y Soc. 1925 21). Owing to the nature of the investigation it was necessary to obtain a high order of accuracy. A detailed survey has been made of the alteration in the electrical conductivities and the degree of dissociation of these electrolytes over a wide range of dilutions in solvents ranging from pure water to the acetonewater mixture containing only 5 volumes of water in 100 volumes of the mixed solvent. Conductivity measurements have been wade for hydrogen chloride in water and eight mixtures of acetonewater and for potassium chloride in water and six acetone-water mixtures at 30" and 25" and at dilutions ranging from 10 to 10,OOO litres per gram-molecule.E X P E R I M E N T A L. Materials .-Acetone was dehydrated over fused calcium chloride and distilled fractionally at least twice immediately before use, care being taken to avoid contamination from the air. The acetone distilled between 56.2" and 56.3" a t 760 mm. and none with a specific conductivity greater than 0.5 x 10-7 mho. at 20" was used. This acetone compares favourably with that obtained by other investigators (e.g. Dutoit and Levier J . Chim. Phys. 1905 3 435; K 0.5-2.0 x 10-7 mho. at' 20". Benz Dissertation Lausanne, 1905; K 0.22 x mho. at 18"). The water was prepared from high grade distilled water by a double distillation and had a specific conductivity less than 1-2 x 10-6 mho at 20" 2924 BROWNSON AND CUY THE ELECTRICAL CONDUCTIVITIES The hydrochloric acid was prepared in normal solution and its strength determined gravimetrically from time to time.The potassium chloride (A.R. quality) was recrystallised three times from conductivity water heated for some hours at 120" and kept in a vacuum desiccator. Standard solutions were made up as required by direct weighing and standardised against silver nitrate. Prepration of Solutions.-All mixtures of acetone and water were made up to contain the specified volume of water in 100 volumes of the mixed solvent the final volume adjustment being carried out at 15". Great care was paid to this dilution on account of the considerable contraction in volume (Reilly Proc. Roy. Dublin Soc., 1919 15 43) and change in temperature which take place upon mixing acetone and water.In each series of conductivity measurements the most con-centrated solution and occasionally the more dilute solutions of hydrogen chloride and potassium chloride were prepared in a manner similar to the above the requisite volume of acid or salt solution replacing an equivalent volume of water. Subsequent dilution was carried out using specially standardised flasks and pipettes. This method was considered preferable to direct weighing on account of the vohtility of the acetone. All measurements were carried out on the same day as the solutions were made up and these were kept in the dark until actually required. The range of dilutions covered in the case of potassium chloride was limited by its sparing solubility especially in solvents rich in acetone.The electrical conductivities were measured at dilutions up to 10,OOO litres except in solvents with a high water content; the highest dilution was then 2,500. A pawatus.-The usual type of Kohlrausch apparatus modified as described below was used with a thermionic valve oscillator as the source of alternating current and with the telephones across the ends of the bridge wire (Schlesinger and Reed J. Amer. Chem. SOC., 1919 41 1'727). The bridge wire calibrated by the method of Strouhal and Barus and of accurately measured resistance could be extended a t either end by means of non-inductive standard resistance coils. The other arms of the bridge contained a standard resistance box and the electrolytic cell respectively whilst two variable air-condensers were arranged in parallel so that they could be connected in parallel across either arm of the bridge as required, in order to balance the capacities in the system.All connecting wires were of stout copper and of known resistance, which was corrected for when necessary OF HYDROQEN OHLORIDE AND POTASSIUM CHLORIDE ETC. 2925 The thermostats were regulated to & 0.05" by means of Lomy regulators with electrical control and all metal parts were earthed. Source of Current.-Taylor and Acree ( J . Amer. Ckm. SOC. 1916, 38,2415) have shown that the resistance of an electrolyte in aqueous solution measured between platinised electrodes of half-inch diameter alters with frequency up to 600 cycles but that there is no change of resistance at high frequencies which were investigated up to 2,000 cycles.Preliminary work on these acetonewater mixtures with an induetion coil as the source of alternating current showed that accurate reproducible results were unobtainable on account of the lowness and inconstancy of the frequency together with the unsym-metrical and irregular nature of the current. This source of current was therefore discarded in favour of a Sullivan thermionic ealve oscillator the frequency of the alternating current being readily adjustable by means of the anode condenser. The frequency used in this investigation was 1060 cycles which was sufficiently high to reduce the possibility of polarisation in the cell and also gave a note readily detected in the telephones.A cathode ray oscillograph was used to ascertain whether the current had a pure sinusoidal form. No difEculty wzts experienced even at the highest dilutions in obtaining an excellent minimum in the telephones when the resist-ances and capacities were accurately balanced. Conductivity CeZZs.-Taylor and Acree (Zoc. cit.) have shown that in aqueous solution whilst there is no change of resistance with change in frequency when platinised electrodes are used at fre-quencies above 600 cycles there is a fall in resistance with increasing frequency when plain platinum electrodes are used. When these results are extrapolated to infinite frequency the resistance measured with plain electrodes is identical with that found at the lower frequencies with platinised electrodes.A preliminary survey of the behaviour of electrodes in acetone-water mixtures showed that the resistances of solutions measured with plain electrodes were higher than the resistances of the same solutions measured with platinised electrodes but that the dis-crepancy between them decreased as the resistance of the solution being measured increased. Thus in the acetonewater mixture containing 10% by volume of water the results obtained at the higher dilutions with either electrode surface were substantially identical. The possibility of error due to the catalytic action of the platinum black on the acetone was investigated in a series of experiments in which the specifh conductivities of hydrogen chloride solution containing one gram-molecule in 20 500 aiid 5,000 litres of 96 5 acetone-water were measured a t 20" for periods up to 50 minutes, during which time the current was passing through the cell.The maximum alteration in specific conductivity of these solutions over this period was & 0.15y0 at the highest dilution but as the changes were in the direction of both increased and decreased specific conductivity any alteration was ascribed to temperature fluctu-ations and experimental error in determining the bridge setting. The conclusion is drawn that the use of platinised platinum electrodes is not attended by objection in acetone-water mixtures on account of catalytic action of platinum black on the solvent. Three cells having cell constants 0.5703 0.4686 and 0.1686 were used for the measurement of the specific conductivities of the electrolyte solutions.The standard solution for determining these constants was 0-02N-aqueous potassium chloride ; its specific conductivity at 25" being taken from the results of A. C. Melcher (Noyes and Falk J. Amer. Chem. Soc. 1912 34 454). The cell constants were checked a t frequent intervals during the course of the research and wherever possible the conductivity of a solution was measured in two cells having respectively low and high cell constants. The cells were all of the same type consisting of a tubular borosili-c a b glass vessel closed by means of a stopper and fitted in each case with lightly platinised platinum disk electrodes 1 cm. in diameter mounted vertically on stout platinum leads which were carried through the walls of the vessel into side tubes containing mercury.Solvent Correction and Calculation of the EquiGalent Conductivity at Infinite Dilution.-The corrections which should be applied to values of the specific conductivities of electrolytes on account of the conductivity of the solvent itself have been discussed by several investigators. Kendall ( J . Amer. Chem. Soc. 1917 39 7) has summarised the position and concludes that if the solvent is of sdliciently high degree of purity no correction need be applied in the case of acids stronger than acetic acid throughout the ordinary range of dilution but that where the electrolyte is the salt of a strong acid and strong base substantially accurate values are obtained by the procedure of Kohlrausch namely direct subtraction of the whole of the solvent conductivity.The dissociation constant calculated for hydrogen chloride from conductivity measurements falls as the percentage of acetone in the mixed solvent increases but even in the solvent containing 5 volumes of water in 100 volumes of acetone-water it is approx-imately 6 >- at 2.5" compared with 1.8 x 10-5 a t 25' for aceti OF HYDROGEN CHLORIDE AND POTASSIUM CHLORIDE ETC. 2927 acid in water. Consequently no correction has been applied on account of the conductivity of the solvent itself to the values obtained for hydrogen chloride in these acetonewater mixtures but in the case of potassium chloride the whole of the solvent conductivity has been aubtracted. In all cases the specific conductivity of the solvent was small in comparison with that of the electrolytes even a t the highest dilutions.The values for the equivalent conductivity at infinite dilution have been calculated by the method suggested by Washburn ( J . Amer. Ckm. Soc. 19!8 40 122) from the equivalent con-ductivities at the highest dilutions measured the value of the mass-action expression A ~ / A ~ ( A ~ - &)?I being plotted against the concentration for various assumed values of Am and that figure for A being taken as the most probable which led to no abrupt rise or fall in the curve at the highest dilution. The degree of dissociation of the electrolytes has been obtained from the expression a = h/h, no account being taken of the change of viscosity with dilution.RWUlts. The influence of variation in the composition of the solvent will be shown to be extremely marked in acetone-water mixtures of high acetone content especially in the case of the more concentrated electrolyte solutions. Thus alteration in the water content from 5 to 10% by volume is accompanied by a lOOyo change in the equivalent conductivity at dilution v = 50 and by a 2.5% change atv = 10,OOO. The measurements in all acetone-water mixtures were repeated several times with different samples of acetone. Thus, in the case of hydrogen chloride in the solvent containing 10% by volume of water nine separate series of measurements at all dilutions were made with different samples of acetone. The results given in all cases are the mean values.In the solvent mentioned the variation from the mean of these nine series of results over all dilutions wm & 0.5% and the reproducibility in solvents richer in water was of considerably higher degree of accuracy. In the solvent containing 50% by volume of water the variations were only 3 0.2% the results in the different series being in the same relative order a t all dilutions. A series of at least fen measurements with different bridge settings was made for every solution the maximum divergence from the mean being generally less than 5 o.05y0. Owing to the considerable difficulties in obtaining really accurate values in pure acetone due particularly to the marked effect o 2928 BROWNSON AND CRAY THE ELECTRICAL CONDUCTIVITIES TABLE I. Equivalent conductivities of hydrogen chloride in metone-water mixtures cat 25".Volume yo of water V 10 20 25 M) 100 250 500 1,000 2 m 5,000 10,000 K of solvent mho x lo-. Q) 5 10 - 2049 13.76 - - 30-81 19.70 38.93 26.15 48.42 37.50 63-40 48.08 73-96 60.39 83-13 77-47 93.16 88.41 98.22 97.61 101-5 012.2) (105.5) h 0.054 0-11 20 51-49 63-93 72.88 80.55 91.40 96-66 -100.8 104.9 106-4 107-7 (109.1) 0.20 35 50 99.44 149.7 110.1 158-0 116.9 162-7 122.6 167-3 129.0 172-5 132.2 174.2 133.8 175.4 135-8 175.9 137.0 176.3 137.7 176.5 038.5) (176.8) 0.30 0.44 - -65 202.1 211-0 215.9 219.7 224.3 225.8 226-6 227.3 227.5 (227.8) 0.55 --80 2 70.1 281.6 286-8 290.3 293.3 295.0 296.4 297.3 -- -(297.9) 0.75 -.90 100 321.3 389.9 332.0 401.0 336.0 406.4 341.0 411.0 344.2 415.3 346-6 418.0 348.0 419.5 348.9 420.7 - -- - - -(349.6) (422.0) 0.85 1.0 TABLE II. The equivalent conductivities of Aydrogen chloride in acetone-water mixtures at 20". Volume % of water. / 1 \ 2). 5. 10. 20. 35. 50. 80. 100. 10 - 19.70 47.86 90-77 135.7 247.0 362.5 20 13.21 -25 - 28.77 59.02 100.4 143.1 257.6 372.5 50 18.97 36.55 67-20 106.4 147.1 262-4 376.9 100 25.05 45-37 74-24 111.7 161.1 265.1 380-6 260 35.90 59.29 84.10 117.3 155.6 267-8 384-5 500 45-88 69.00 88.60 119-9 157.1 269.4 387.2 1,OOO 67-54 77.28 92.35 121.3 158.1 270.4 388.1 2,500 73.55 86-50 96-10 123.0 158.6 271.3 389.6 - - - - -6,000 83.80 91-25 97.25 123.7 158.9 - -10,OOO 92.56 94.40 98-40 124.5 159.1 - -in mhox 10" a (106.4) (98.0) (99-7) (125.2) (159.3) (272.0) (390.6) K of solvent 0.049 0.09 0.18 0.26 0.40 0.68 0.90 TABLE 111.The equivalent conductivities of potcassiunt chloride in acetone-water mixtures at 25" Volume yo of water. 0. - _ _ _ ~ U. 5. 10. 20. 35. 50. 65. 10'0. 50 - - 53-20 59-75 67-45 80.40 138.6 100 - 58.90 60.32 64.47 70-80 82.09 141.6 250 - 72.95 68.50 68-49 74-02 85.20 145.2 500 - 82.50 73-20 70-95 75-70 86-00 146.7 1,000 98.39 89.00 76-54 73.00 76-61 86.70 147.7 2,000 108.1 2,500 - 98-80 79-80 74-65 78.00 87-76 149.1 5,000 117.9 99.15 81-30 75-90 78.64 88.40 -10,000 122.4 101.3 82.50 - - - -al (127-7) (103.7) (84-50) (77.30) (79.40) (89.10) (150.1) K of solvent 0-054 0-11 0.20 0.30 0-44 0.66 1-0 in mho x l(r - - - - - OF HYDBOGEN CHLORIDE AND POTASSIUM CHLOBLDE ETC.2929 TABLE TV. The equicalent conductivities of potassium ch,?rn.de in acebne-woter nixtures at 20". Volume yo of water. r V. 5. 10. 20. 36. 60. 66. 100: 50 - - 48.81 53-81 60-00 71-27 125-5 100 - 55.06 55.20 57-81 63.02 72.78 128.2 250 - 68.13 62.60 61.39 65.80 75.28 131.0 500 - 76-40 66.85 63.60 67.10 76-05 132.1 1,000 92.31 82-28 69.91 65.42 68.01 76.70 132.9 2,000 101.5 -2,500 - 88-40 72-75 66.60 69.03 77.50 134.3 5,000 110.2 91.70 74.00 67.70 69.65 78.00 -- - - - -10,000 114-3 93.60 75.30 - - - -00 (119.1) (95.7) (76.90) (68.90) (70-3) (78.60) (135.2) K of solvent 0-049 0-09 0.18 0.26 0.40 0.50 0-90 in d o x 10-6 TABLE V.The epuiz.alent corzductivities of bydrogen c h i d e in water at 18" and 25" and of ptmsiurn chlm'de at 25". Hydrogen chloride. 2). 10 25 50 100 250 500 1000 2500 M Goodwin and Haskell This (inter- This rewarch. polatad). research. 351.7 351.4 389-9 362.0 - 401.0 364.9 365.5 406.4 368.5 369.2 411-0 372.3 373.6 415.3 374.9 375.0 418.0 375.8 375-9 419-5 377.2 - 420.7 (378.2) - (422-0) Bray and Hunt (intar-polated). 390.4 400.7 406-7 41 1.6 416-4 418-6 419.0 -Potassium chloride. 25O. w-Lorenz This (inter-research. Melcher. polated). - 129.0 -135.4 - 135.1 138.6 138-65 138.6: 141.6 141.4 141-6 145.2 - 144.75 146.7 146.5 146.55 147.7 - 147-76 149.1 - 149.22 (150.1) (150.6) -even the slightest trace of water this solvent has not been studied in this investigation.Results can be extrapolated for pure acetone from the values given but it is hoped in the future to investigate the problem experimentally as the only data available are very incomplete (Carrara Gazzetta 1897 27 i 207; Sackur Ber. 1902, 35 124s). The values for hydrogen chloride are all observed values being uncorrected and those for potassium chloride corrected by sub-traction of the solvent conductivity. Kendall ( J . Amer. C h m . Soc., 1917 39 7) gives 379.1 as the most probable value of A for hydrogen chloride in water at 18" and 422.7 at 25". References.-Goodwin and Haskell Physical Rev. 1904 19, 380. Melcher Bray and Hunt J . Amer. Chem. Soc.1911,33 781 2930 BROWNSON AND GRAY THE ELECTRICAL CONDUCTIVITIES see Noyes and Falk ibid. 1912 34 154. 1921,116 161. Lorenz 2. avgew. Cherr~., Discussion. The Influence of the Solvent on the Equident Conductivity of PotcGssiurn ClUoride and Hydrogen ChEoride.-The influence FIG. 1. I I I I 0 10 20 30 40 f of the ~ ~ i 30 100% acetone. Volume yo of water. 0% acetone. solvent upon the equivalent conductivity of hydrogen chloride in these acetone-water mixtures is extremely marked (fig. 1). Accord-ing to the classical theory of electrolytic dissociation this arises from two causes ; first the effect of the solvent upon the migration velocities of the individual ions and secondly upon the degree of dissociation of the electrolyte. The equivalent conductivity at infinite dilution falls rapidly as water is replaced by acetone up t OF HYDROGEN CHLORIDE AND POTASSIUM CHLORIDE ETC.3931 about 85% of acetone by volume followed by an increase of con-ductivity in acetonewater mixtures richer in acetone. The effect of alteration in the degree of dissociation of the electrolyte is shown by the equivalent conductivities at finite dilutions and accounts for the pints of idexion in the equivalent conductivity-composition of the solvent curves (Fig. 1) at the acetone-water mixture containing 10% by volume of water where the solvent has a marked effect iipon the degree of dissociation of the electrolyte (Fig. 3). FIG. 2. t i Ti A 1 90 loo D I 0% a,cetone. The nature of the equivalent conductivity-composition of the solvent curves for potassium chloride in acetone-water mixtures differs greatly from the case of hydrogen chloride.The equivalent conductivity at infinite dilution falls to a minimum in the solvent containing 40% by volume of water (Fig. 2) but owing to the effect of the fall in degree of the dissociation of this electrolyte with increase in acetone content of the solvent (Fig. 4) this minimum changes with dilution and indeed in the case of dilutions v = 50; v = 100 no minimum is observable within the limited range of acetone-water mixtures which can be studied at those concen 2932 BROWNSON AND CRAY THE ELECTRICAL CONDUCTIVITIES trations on account of the low solubility of potassium chloride in mixtures rich in acetone. Numerous investigators have attempted to show the dependence of the equivalent conductivity at infinite dilution on the physical properties of the solvent.Hartley Thomas and Applebey (J. 0 10 20 30 40 50 60 70 80 90 100 100Yo acetone Volume yo of water. 0% acetone. 1908 93 538) on the assumption of the applicability of Stokes' law to an ion moving with a spherical solvent atmosphere sur-rounding it have shown that if the ionic radii of the anion and kation respectively do not vary with the composition of the solvent, then A,q = constant where 7 is the viscosity of the solvent. Walden (2. physikd. Chem. 1906 52 242; 1911 78 273 278, etc.) has shown that the product A,? is constant and independen OF HYDROQEN CHLORIDE AND POTASSITJM CHLORIDE ETC. 2933 of the temperature for tetramethylammonium iodide tetrapropyl-ammonium iodide potassium iodide and other organic salts in a large number of organic solvents but he has also shown that solvents with large association fact,ors and high dielectric constants give variations from this rule.Creighton ( J . Franklin Inst. 1919 187, 33) found that deviations were shown by trimethyl-p-tolylammonim iodide in several organic solvents. The viscosities of acetone-water mixtures rise to a maximum in the solvent containing approximately 60% by volume of water (Davis Hughes and Jones 2. physikd. Chm. 1913 85 535), whereas the equivalent conductivity at infinite dilution of potassium FIG. 4. 100 yo acetone. Volume yo of water. 0% acetone. chloride in acetone-water mixtures has been shown in the present research to be a minimum in the solvent containing 40% of water by volume.No constancy of the expression 1-7 caa be expected. The equivalent conductivity of the electrolyte at inhite dilution is therefore dependent not only on the viscosity of the solvent but also on its other physical properties for example its state of associ-ation and dielectric constant. In aqueous solutions the conductivity of hydrogen chloride is exceptional owing to the high value of the mobility of the hydrogen ion. In acetone-water mixtures of high acetone content however, the mobility of the hydrogen ion does not d8er greatly from that of the potassium ion as the equivalent conductivity of hydrogen chloride a t infinite dilution is only slightly higher than that o 2934 BROWNSON AND CRAY THE ELECTRICAL CONDUCTrVlTIES potassium chloride in the acetone-water mixture containing 10% by volume of water.In the solvent containing 5% by volume of water it is actually smaller. The Influence of the Solvent on the Degree of Dissociation.-The influence of the solvent upon the degree of dissociation of electrolytes has been formulated in the well-known Nernst-Thomson rule. Bruhl (2. physih?. Chem. 1899 30 1) has pointed out that no absolute proportionality can exist between the dissociating power and the dielectric constant of the solvent as the latter varies greatly with temperature and also with frequency. The values of the degree of dissociation of hydrogen chloride and potassium chloride calculated from the expression a = &,/A are in Table VI and the influence of the solvent is shown in Figs.3 and 4. The influence of temperature upon the degree of dissociation of the electrolytes in acetone-water mixtures is as would be expected, more marked the greater the concentration and the smaller the degree of dissociation of the electrolyte and the dielectric constant of the solvent. TABLE VI. The degree of dissociation of hydrogen chloride and phsirr.m chloride Hpdrogen Chloride. in acetone-water mixtures at 20" and 25". Volume of water ~ - - - - - __ - - __ __ - r-5 I0 00 35 50 80 100 SOo 25" 20" 25' -00" "5" 20" 25' 00" 25O 20" 35O. 20'. 25O 10 - - 0.201 0-198 0-480 <-472 0.725 0-718 0-852 0-847 0.908 0-906 0-928 0.925 25 - - 0.295 0.29% 0.592 0-586 0.802 0.795 0.899 0.894 0-947 0.945 0.953 0.950 50 0.178 0.176 0-373 0.369 0.674 0.668 0.850 0.844 0-923 0-920 0.965 0.963 0.965 0.963 100 0.236 0.233 0.463 0.459 0-744 0.738 0.892 0.885 0.949 0.946 0.975 0.974 0.974 0.974 250 0.337 0.334 0.605 0.601 0.843 0.838 0.937 0.931 0.977 0.975 0.984 0.984 0.984 0-984 500 0431 0.428 0.704 0.701 0.889 0.885 0.958 0.954 0-986 0.985 0.991 0.990 0.991 0.991 1,000 0.541 0.538 0-789 0.788 0.926 0.924 0.969 0.966 0.993 0.992 0.994 0-995 0-994 0.994 2,500 0-691 0.690 0-883 0.883 0.964 0.962 0-982 0.980 0-996 0.995 0.997 0.998 0.997 0.997 5y000 0-787 0.788 0.931 0.931 0-975 0-975 0-989 0.989 0.998 0.997 - - - -10,000 0.870 0.870 0.963 0.962 0.987 0-987 0.994 0-994 0-999 0.998 - - - -2' A - 7\ +- 4 Potanssium Chlm.de.Volume "/b of water. 50 100 250 500 lyoOO 2,500 8,000 1!J,Vo0 I 0.775 0.925 0.960 -050 800 250 yo0 "0 - - _ 0.635 0-630 - U*t75 0-568 0.718 0.714 - U-rl2 0-704 0-814 0.811 - 0.798 0.796 0-869 0-866 0-770 0-860 0.858 0.909 0.906 - 0.924 0.924 0-946 0.944 0.923 0-958 0.956 0-962 0.962 0.958 0.978 0.977 0.979 0.980 U-891 0.886 0.936 0.923 0-918 0.954 0.949 0.944 0.967 0-967 0.966 0.982 0.983 0.988 0.991 - - -250 0.850 0.892 0-938 0.954 0-965 0-982 0.990 -20" 25" 0.907 0.902 0.926 0.921 0.958 0-956 0.968 0-965 0.976 0.973 0.986 0.985 0.992 0-992 - -'OD 250 0.928 0.923 0.948 0.943 0.969 0.967 0.977 0.977 0-983 0.983 0-994 0.993 - -- -The values of the Ostwald expression G/(l - a)v show consider-able alteration with dilution in water or acetone-water solvents an OF HYDROGEN CHLORIDE AND POTASSIUM CHLORIDE ETC.2935 in no case is a true constant obtained but in mixtures rich in acetone the change with dilution is much less marked. Summary. (1) The electrical conductivities of hydrogen chloride and potas-sium chloride have been measured over a wide range of dilution at 20" and 25" in acetone-water mixtures containing from 5 to 100% of water by volume. The equivalent conductivity of hydrogen chloride a t infinite dilution falls sharply to a minimum in the solvent conhining about 86% of acetone after which the change is small an increase being noticed in solvents very rich in acetone. In other solutions the equivalent conductivity falls as the acetone content increases as the result of the influence of the solvent upon the degree of dis-sociation of the electrolyte as well as upon the migration velocities of the individual ions. The equivalent conductivity of potassium chloride a t infmite dilution falls to a well-defined minimum in the solvent containing approximately 40% by volume of water but a t other dilutions, owing to the change in degree of dissociation of the electrolyte this minimum shifts and in more concentrated solutions w = 100 and u = 50 no minimum is observable in any acetone-water mixture in which the solubility of this electrolyte allows the measurement to be made. (2) It is shown that the use of platinised platinum electrodes is not attended by error due to catalytic influence upon the acetone in the mixed solvents studied. (3) The influence of temperature upon the degree of dissociation of these electrolytes is more marked the higher the acetone content of the solvent and the higher the concentration of the solution. ( 4 ) The Ostwald dilution law does not hold fully in any acetone-water mixture investigated but as the acetone content increases, gives values more nearly approaching a constant a t all dilutions. We wish to express our indebtedness to Dr. G. Rotter C.B.E., and Dr. J. N. Pring for t-heir interest in this work which is published by permission of the Director of Artillery War Office. RESEARCH DEPARTMENT, ROYAL ~ E N A L WOOLWICH. [Received Azrgwrt Zlet 1925.

ISSN:0368-1645    

DOI:10.1039/CT9252702923

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

2936 REILLY AND MADDEN THE VELOCITY OF DECOMPOSITION CCCCVI.-The Velocity of Decomposition of Heterocyclic Diamnium Salts. Part I . Diaxonium Xalts of the Pyraxole and Pyrazolone Series. By JOSEPH REILLY and DENIS MADDEN. HITHERTO so far as the authors are aware no quantitative measure-ments of the stability 01 heterocyclic diazonium salts have been made. Qualitative examination has shown that aminopyrazole and amino-pyrazolone compounds form a very distinct group and therefore, an investigation has been made in the first instance of the com-parative stability of these substances under certain conditions. The FIG. 1. physicochemical method of Hausser and Miiller (Bull. Soc. chim., 1892 7 721) or the modification of it devised by Cain and Nicoll (J. 1902,81,1412) wm found unsuitable for this particular problem, owing fo the extraordinary comparative stability of some of the compounds examined and the consequent exceptionally long period of time during which the reaction had to be followed.The process adopted by the authors mas to heat a definite volume of a solution containing a known weight of the amine (sufficient to give 56 C.C. of gas at S.T.P. normal diazotisation being assumed) in a specially constructed quartz vessel A (Fig. l) fitted with a ground stopper into which was sealed a tube passing to the bottom of the vessel. The vessel was containecl in a thermostat B at 101-5" which temperature was found to keep the solution of the diazonium salt a t lOO" and was connected through a condenser C to a water-jacketed nitrometer D.A current of air-free carbon dioxide wa OF IEETEROCYCLIC DIAZONrtJM SALTS. PART I. 2937 periodically passed through the solution and the liberated nitrogen waa collected over concentrated aqueous potassium hydroxide. By this method it is possible to overcome the diEculties met with by earlier investigators. The air is completely expelled from the apparatus the vessel containing the solution is placed in the thermo-stat and a current of carbon dioxide is passed through it until the temperature becomes constant (the necesmy time having been determined in a control experiment); the nitrogen evolved during this time is collected and measured. It is thus possible to have an exact starting point for a solution of definite concentration. Further, no allowances such as had to be made by former investigators are necessary for the expansion of the solution and of the air in the apparatus.(The appstratus is so arranged that the air space between the surface of the solution and the mercury in the nitrometer is as small as conveniently possible.) 1-Phenyl-2 3-dimethylpyrazolone-4-diazonium ChEoride (Anti-pyrine-Pdiamium C h i d e ) .-A solution of 0.5075 g. of 4-amino-antipyrine in air-free water and 7.5 C.C. of N-hydrochloric acid (3 equivs.) was treated with 20 C.C. of aqueous sodium nitrite (1.73 g. per 200 c.c.) and the resulting solution made up to 70 C.C. The solution of the diazonium salt originally pale yellow developed a reddish-brown colour on warming. This evidence of a secondary reaction is supported by the fact that after 90% of the substance had de-composed the rate of gas evolution declined rapidly.The decom-position however was mainly a unimolecular reaction. In the table x = the volume of nitrogen evolved after t hours (measured a t 22" and 766 mm.) and k = l / t . log (a/(a - z)) where a = the theoretical volume of " diazo "-nitrogen under the same conditions (= 60 c.c.). t. 2. k x lo3. 0 0.2 -1 8.0 62.15 2 13.4 64-80 3 18.2 52.32 4 22.7 61-61 5 27.0 51.93 6 30-8 52-13 t. x. k x lo5. t* x. k x lo3. 7 344 52-84 14; 49.6 52.50 8 37.5 53-20 15Q 50-5 51.60 9 40.1 53.20 51.2 50.60 10 42.4 53.31 i;i 51-8 50.00 11 44.3 53-00 53.0 46-00 12 46.1 62-93 zi 53-4 -13 47-7 53-00 Neither the addition of excess of mid nor the introduction of a small amount of colloidal gold had any marked effect on the rate of decomposition.Antipyrine-4-diazonium A'itrute.-The rate of decomposition was of the same order as that of the chloride. The amount of secondary reaction was however slightly greater the rate of gas evolution falling off more rapidly towards the end. Antipyriue-4diamizcm Su1phate.-The rate of decomposition w~b 2938 REILLY AND MADDEN THE VELOCITY OF DECOMPOSITION much more rapid a t the beginning and did not follow the uni-molecdar law the value of k falling from 0.1305 (8 C.C. in the h t 8 hour) to 0.0544 (38.8 C.C. in 9 hours) ; a behg 57.35 C.C. That the amount of secondary reaction was considerably greater was shown by the more marked deepening of colour and the formation of a dark reddish-brown precipitate.The rate of decomposition then is in this case considerably influenced by the nature of the anion unlike the results obtained by Cain (Ber. 1905 38 2511) with benzenoid diazonium salts. ChEoride.4-Amino-3 ; 5-di-methylpyrazole (0.2775 g.) was dissolved in 15 C.C. of N-hydrochloric acid (6 equivs.) and treated as in the foregoing cases. The amount of decomposition in 3 hours was almost inappreciable less than 2% of the total " diazo "-nitrogen being evolved. In a second experiment, 3 equivs . of acid being used the decomposition followed the peculiar course indicated by the following figures : Temp. = 18". 3 5-Dimethylpyrazole-4-diazonium Pressure = 756 mrn. Q = 60 C.C. t ............... 0 1 2 3 4 5 6 7 z ...............0.0 1-0 2-4 4-2 6.0 7.8 9.7 11-6 t ............... 8 9 10 11 12 14 16 1s x.... ........... 13.6 15.4 17-4 19.4 21.4 25.0 28.7 32.1 t ............... 20 24 28 32 36 40 44 48 x ............... 35.0 40-6 45-4 49-3 52.1 54.6 56.2 57-2 These figures show that even after 48 h o ~ ' heating the decom-position of the diazonium salt is not complete. It is evidently irregular a t the beginning less nitrogen being evolved during the first hour than during any of the subsequent 20 hours. This be-haviour is probably due to the existence of two isomeric forms of the diazonium chloride and this view is supported by the fact that when a small quantity of the base is diazotised a t the ordinary temperature and added to alkaline p-naphthol no coupling takes place for some time whereas a colour is immediately developed if the diazonium solution has previously been boiled for a few minutes.After the fourth hour the decomposition proceeds with some degree of regularity but not in accordance with the unimoleculax law. 3 5-Dimethylpyrazole-4-diazonium Su1phate.-As in the case of the chloride the reaction was irregular a t the beginning. From the end of the fourth hour to the end of the twelfth hour the rate of decomposition followed the unimolecular law the mean value of k being 0-0720. A solution of the diazonium salt containing an excess of sulphuric acid (6 equivs.) was remarkably stable only 2% of the total " diazo "-nitrogen being evolved in 3 hours. Pyrazole-4-diazonizcm Chloride.-3 5-Dimethylpyrazole was con-verted by Knorr's method (Annulen 1894,279 218) into the corre OF HETESOCYCLIC DIAZONIUM SALTS.PABT I. 2939 sponcling 3 5-dicarboxylic acid the latter however being isolatd from the oxidation product by the addition of hydrochloric acid without the intermediate formation of the acid potassium mlt. Pyrazole obtained by heating the dry dicarboxylic acid at 270-275* was converted by Buchner and Fritsch’s method (An&, 1893 273 265) into the 4-nitro-compound. This was isolated by adding ice to the nitration mixture and was reduced as follows : A solution of 3 g. of the nitropyrazole in 100 C.C. of moist ether waa treated with cooling with a large excess of an aluminium-mercury couple during a few hours complete reduction being indicated by FIG. 2. 4 8 12 16 20 24 28 32 36 Time of heating (hour8).I o-Nitrobenzenediaumium chloride. 11 Pyrazole-4-diawnium chlopide. III 1 -Ph.elenyl-2 3-dillaethylw~zololae-4-diazonium cJdoride. IIIa l-Phenyl-2 3-dimethybpymzolone-4-diazm~um 8 u l p W . IV 2 3-Dimethylp~azoie-4-dkzoniwn c h l u d e . N o 2 3 - D i m e t h y l p ~ a ~ e - 4 - d i a ~ ~ i ~ ~ d p h a t e . the disappearance of the purple colour initially developed. The ether was distilled off the residue extracted a few times with boiling alcohol air being excluded and the extract was immediately treated with hydrochloric acid. The product was evaporated, and the residue recrystallised from alcohol ; 4-aminopyrazole dihydrochloride then separated. As the quantity obtained was small the somewhat dark product was not further purified before diazo tisation.The rate of decomposition of the diazonium chloride from 0.39 g. of the dihydrochloride approximately obeyed the unimolecular law. In 5 hour^ 83% of the total “diazo”-nitrogen was evolved but thereafter the rate of decomposition declined very rapidly. The much more rapid decomposition of this substance seems to indicate VOL. cxxm. 5 2940 U D L E S THE SWELLING AND DISPERSION OF that the methyl groups in diazotised 3 5-dimethylaminopyrazole have a slabiliaing influence on that diazonium salt. The comparative stability of the diazonium chlorides from 4-aminoantipyrine 4-amino-3 5-dimethylpyrazole and 4-amho-pyrazole may be judged from the curves in Fig. 2 showing the rate of gas evolution at various intervals. Of the large number of benzenoid diazonium salts investigated by Cain and Nicoll (Zoc.cit.) the most stable (and the only two apparently sufficiently stable for examination a t 100") were those from 0- and m-nitroaniline. The conditions under which the experiments described above were carried out were different from those employed by earlier investigators but results closely analogous to those of Cain and Nicoll were obtained in a control experiment in which o-nitroaniline was used. A comparison of the results obtained from the diazonium chlorides in the pyrazole and pyrazol-one series with those from 0- and m-nitroaniline is therefore justifi-able (for 4-amino-3 5-dimethylpyrazole the results are the mean of the experiments in which only 3 equivalents of hydrochloric acid were used in the diazotisation). Time (mins.) k (t measured yo Decomp. for half de-Substance. in mins.). in first hr. composition. m . Ni trotmiline ........................ 0-03 3 2 100 10 o-Nitroaniline ........................... 0.00564 54 53 4-Aminopyrazole ..................... 0.003 17 40 80 4-Aminoantipyrine ..................... 0.0008 8 13 360 4-Amino-3 5-dimethylpyrazole ... 0.00030 1.7-2 1020 In the case of 4-amino-3 5-dimethylpyrazole the rate of decom-position of the diazonium chloride was considerably slower (3 to 4 times) when excess of acid (6 equivs.) was employed. It cannot be said as of benzenoid salts that the rate of decomposition in the case of heterocyclic diazonium salts is uninfluenced by the nature of the anion for the diazonium sulphates of both 4-aminoantipyrine and 4-amino-3 5-dimethylpyrazole decomposed much more rapidly than the corresponding chlorides. UNIVEIWITY COLIXGE CORE. [Received September 7th 1925.

ISSN:0368-1645    

DOI:10.1039/CT9252702936

出版商:RSC    

年代:1925

数据来源: RSC