416 CLARKE: THE RELATION BETWEEN REACTIVITY ANDXLVI.-The Relation between Reactivity and ChemicalConstitution of Certain Halogen Compounds.By HANS THACHER CLARKE.THE reactivity of the halogens in organic halogen compounds hasbeen studied by various investigators : Wislicenus (Annulen, 1882,212, 239), with ethyl sodioacetoacetate ; Hecht, Conrad, andBriickner (Zeitsch.. physikal. Chem., 1889, 4, 273), with sodiumethoxide ; Menschutkin (Zeitsch. physikal. Chem., 1890, 5, 589),with triethylamine; Burke and Donnan (Trans., 1904, 85, 555;Zeitsch. physikal. Chem., 1909, 69, 148), with silver nitrate; Slator(Trans., 1904, 85, 1286; 1905, 87, 482), Slator and Twiss (Trans.,1909, 95, 93), with sodium thiosulphate; Senter (Trans., 1907,91, 460; 1909, 95, 18271, with water and with alkalis; but nodefinite conclusions appear to have been drawn as to the relationsbetween reactivity and constitution.The present paper deals with compounds of the type X*CH,*R,the object being to study the influence of the nature of the group(R) on the reactivity of the halogen (X).The reactivity was determined by the measurement of thevelocity of the reaction between pyridine and the halogen compoundin absolute alcoholic solution, identical conditions being observedthroughout the series of experiments :TTC5H5N + X*CH,*R = C5H5N<gH2.R.From the scheme representing the reaction, it is evident thatiouic reactions are improbable.Attempts were a t first made with ethylaniline and dimethyl-aniline a t the temperature of boiling alcohol, but it was foundthat the values of ( ( R,” calculated for a bimolecular reaction,decreased with the progress of the reaction, this effect beingdoubtless due t o “ heterospasis ” :NPhMe, + X*CH2*R-+NPhMe,X*CH,*R-+NMePh*CH,*R + MeX.Pyridine was accordingly selected as a tertiary base in which nosuch decomposition could occur.Moreover, as pyridine is morestrongly basic than the above-mentioned derivatives of aniline, thereaction could take place with measurable velocity a t a lowertemper at ur e.Equal volumes of N/2-solutions of pyridine and the halogencompound were mixed and maintained at the temperature of55*6O, afforded by a water-bath surrounded with boiling acetonCHEMICAL CONSTlTUTION OF CERTAIN HALOGEN COMPOUNDS.417under constant pressure, aliquot portions being withdrawn a tintervals and the ionised halogen titrated with silver nitrate. Theconstant was calculated from the usual formula for il bimolecularreaction, namely :1 Ct A'= -.-C , . t c,-C't'In nearly every case the values of R did not vary from thoserequired for a bimolecular reaction by more than experimentalerror.The experimental results are set forth in the following table;they will be discussed in detail on subsequent pages:n-Propyl bromide ..................Benzyl , , ..................Cinnamyl , , ..................Bromoacetic acid .....................Methyl brommcetate ...............Ethyl $ 3 n-Propyl ,, ...............isoPropyl ,, ...............n-Butyl ), ...............tert.-Butyl ,, ...............Phenyl ,, ...............Benzyl ,, ...............Allyl ...............Ethyl B-bromopropionate .........Bromoace tal ...........................Chloroacetamide .....................Chloroscetanilide .....................Bromoacetanilide ..................Diphen ylchloroacetamide ........Chloroacetone ........................Chloroacetophenone ...............Bromoacetophenone ...............Allyl ,) .................................I ?X.R.Br'CH,'EtBr*CH,*CH: CH,Br 'CH,'PhBr'CH,*CH: CH'PhBr'CH,'CO,HBr*CH,'CO,MeBr*CH,'CO, E tBr'CH2*00,PraBr-CH,* CO, PrsBr'CH,*CO,'CH,*CH,EtBr 'CH,'CO,'CMe,Br*CH,'CO,PhBr'CH,*CO,'C H,PhBr'CH2'CO;C3H,Br.CH,'CH,f!O,EtBr*CH,'CH(OEt),Cl*CH,*CO*NH,Cl*CH,.CO'NHPhBr'CH,*CO*NHPhCl'OH,'CO'NPh,Cl'CH,*COMeC1'CH;COPhBr*CH,*COPhK.0.01791 *2535'1180-4720.6660.9191 '0040-7521 *0480.7700.9341'9271'2110.7680,02770'0120 *011150'02641.5350.03410.06860-13397.269The first fact established was that in a compound of the typeX*CH,*R the reactivity of the halogen, as determined by the abovemethod, was controlled by the residual affinity of the atom orgroup (R) directly attached to the methylene carbon atom.Thefollowing series will illustrate this conclusion :K.n-Propyl bromide .................. 0.0179Methyl brom oacetate ............... 0'919Allyl bromide., ..................... 1 *253Benzyl , , ........................ 5'118Monochloromethyl ether and bromonitromethane were alsoexamined.I n both these cases there are present groups towhich a large amount of residual affinity is attributable (OMe;NO,). Chloromethyl ether reacted so rapidly with alcoholicpyridine that no measurement could be obtained ; whereas bromo418 CLARKE : TlIE RELATION BETWEEN REACTIVITY ANDnitromethane formed a pyridine salt a t once, and very littleelimination of bromine ensued.Taking, then, this rule as a basis, an attempt has been madeto determine the degree of unsaturation in various compounds ofthis type in order to elucidate the nature of the different groupsinvolved.The effect of conjugation of a phenyl nucleus with an ethenoidlinking appears to diminish the total residual affinity inherent inthe carbon atom in the a-position with respect to the methylenegroup, the reactivity of cinnamyl bromide being less than one-halfof thak of allyl bromide:Cinnaiii y 1 bromide ............Ph 'C H: CH *CH, €3 r K = 0 . 4 7 2Allyl )) ............ CH,:CI-I'CH,Rr K= 1.253Turning now to the derivatives of chloro- and bromo-acetic acids,it was found that the reactivity of the halogen varied with thenature of the radicle to which the halogen-acyl group was attached.When equimolecular quantities of pyridine and bromoacetic acidwere mixed in alcoholic solution, it was found, contrary to expecta-tion, that elimination of bromine took place along the lines of abimolecular reaction. This fact would tend to point to the absenceof stable salt-formation in absolute alcohol :Bromoacetic acid ...............K= 0.666The reactivity of the haIogen inaliphatic esters was examined :Methyl bromoacetate ......... 0.919 ......... 1-004 Ethyln-Propyl ,)The phenyl, benzyl, and allyl9 ) ......... 0.752 K- 1examined in the same manner :the following series of saturatedK.1'048 isoPropy1 bromoacetate , . , , , ,~ B ~ t y l ...... 0.770tcrt. -Butyl ), ...... 0'934esters of bromoacetic acid were2 9K. ........... 1.9271 .n*Phenvl bronioscetnte ,. .Betizj.1 ) ) ............. 1,511Allyl .............. 0.768I n phenyl bromoacetate, which exhibits a greatly exaltedreactivity, the alcoholic radicle contains the greatest residualaffinity. In benzyl bromoacetate, in which a methylene group isinterposed between the phenyl and the bromoacetoxyl groups, thecff ect still persists, although considerably diminished. The re-activity of the allyl ester, when compared with that of the n-propylester, shows a slight exaltation-to a less extent, however, owingto the less powerful influence of the ethenoid as compared withthe benzenoid grouping.Since the values obtained from allyl bromoacetate and benzyl2 CHEMICAL CONSTITUTION OF CERTAIN HALOGEN COMPOUNDS.419bromoacetate indicate that the influence of the unsaturated groupis appreciable even when situated in the &position, the reactivityof ethyl P-bromopropionate was measured :Ethyl j3-bromopropionate ................. K=0*0277This value, when compared with the saturated standard, rt-propylbromide (X = 0.0179), is sensibly exalted.Bromoacetal, on theother hand, yields a value (K=0-012) which shows the reactivityof the halogen to be slightly depressed.In the series of halogen-acetylamides, the reactivity of the halogencompounds was measured :K.Cliloroacetamide ............ 0.01 115 Bromoacetanilide ............ 1 -533Chloroacetanilide ............ 0 -0264 Diphenylchloroacetamide . . 0 '0341In the case of the halogen-acetanilides, the reactivity constantof the bromine derivative is 58.1 times as great as that of thechlorine derivative. Taking this ratio, the value calculated fromchloroacetamide yields K = 0.648 for bromoacetamide, a substancedifficult to obtain in a high state of purity, and, moreover,insufficiently soluble in alcohol.The same rule thus holds good for the Br*CH,*CO*O* and theBr*CH2-CO*N: structures, the replacement of hydrogen by phenylgiving rise to increased reactivity of the halogen, as the followingtable shows :K.Bromoacetic acid............... 0'666 (Bronioacetamide ............ 0.648)The reactivities of halogenated ketones were found to be greatlyin excess of those of the corresponding carboxylic compoundsenumerated above :Yhenyl bromoacetate ......... 1 Ir- *927 I Bromoacetanilide ............ 1 -533R.Chloroacetone,. ...................... 0-0686Chloroacetophenone ............... 0-1339Bronioacetopheiione ............... 1'269from which the constant for bromoacetone can be calculated, beingapproximately K = 3.720.I n the case of the ketones, as in the caseof bromoacetic esters, the replacement of a methyl group by aphenyl group occasions approximately doubled reactivity.Two series of measurements were carried out in an aqueous-alcoholic solution (25 C.C. absolute alcohol diluted to 100 C.C. withwater), the substances examined being methyl bromoacetate andpotassium bromoacetate, and the initial concentration of thereacting substances N / 4 before mixing :Methyl bromoacetate ............... 14'61K.Potassium ,, ............... 9 007VOL. XCVII. F 420 CLARKE: THE RELATION BETWEEN REACTIVITY ANDIt will be observed that a far greater velocity of reaction ensuedin the presence of water than in absolute alcohol. The ratiobetween the constants obtained for these substances in aqueous-alcoholic solution is of the same order its that between thoseobtained for methyl bromoacetate and for bromoacetic acid inalcoholic soiution :Methyl broinoacetate (0.919) : broilloacetic acid (0.666) = 1 : 0.7759 9 ,, (14'61) : potassium bromoacetate (9'07) =1 : 0'621It would thus appear that no radical change in constitution occursduring salt-formation and esterification.Discussion of Results.The author inclines to regard the variation of the reactivity ofthe halogen in compounds containing unsaturated groups in theP-position as due to the weakening of the bonds attached to thea-carbon atom caused by the strengthening of the bond betweenthe unsaturated group and the a-carbon atom.To take the caseof ally1 bromide and benzyl bromide, all residual affinity of themethylene carbon atom (*):is absorbed by the unsaturated group, leaving the remaining threeatoms less strongly attached to the carbon atom.This is borneout by the observation of Wislicenus (Zoc. cit.) that the halogen invinyl iodide (CH2:CH*) is subnormally reactive. The subnormalreactivity of the halogens in aryl halides may perhaps be due tothe same cause. This view of the variable strength of affinities withvarying substituents has already been put forward by Claus (Ber.,1881, 14, 432), and fully discussed by Werner and by Flurscheim.Of the compounds containing the halogen-acetyl grouping, thegreatest reactivity of the halogen is to be found among the ketones.This tends to show that the ketonic carbonyl group possesses moreresidual affinity than the carboxylic and carbaniidic carbonyl group.It has long been suspected that in the carboxyl group the twooxygen atoms exert some mutual attraction, and in a recentpublication Miss Smedley (Trans., 1909, 95, 231) has assigned tothe carboxyl group a constitution, *C<g., in which the thirdand fourth valencies of the two oxygen atoms are united.Now, it was shown above that in the case of phenyl bromoacetatethe reactivity of the halogen is approximately double that of thecorresponding methyl ester, and this fact indicates that someinfluence must be at work which transmits the effect through aseries of atoms so as to exalt the reactivity of the halogenCHEMICAL COSSTITUTION OF CERTAIN HALOGEN COMPOUNDS.421Hitherto all formulation of the carboxyl group has beenessentially of a static nature. The old formula, *C<g., must bediscarded, since it furnishes no distinction between the carboxylicand ketonic carbonyl groups, and the formula advocated byGoldschmidt (Zeitsch. Elektrochem., 1904, 10, 221 j, -CiO-O-, isdifficult to reconcile with the chemical and physical properties ofthe group.Miss Smedley’s view of the constitution of the carboxyl groupis in harmony with the results above mentioned, except in so farthat its static nature gives no explanation of the variations inreactivity due to differences in the alcoholic radicle. The authortherefore suggests that this formulation should be modified insuch a way that the greater or less unsaturated character of thecarbonyl group is expressed.Thefirst is that the bond between the oxygen atoms is variable inThere are two possible methods of regasding the problem.intensity, resulting in a formula of this nature: * d o - the \& ’second being that while the attraction between the oxygen atomsremains constant, the bond between the hydroxylic oxygen atomand the carbon atom varies in intensity, requiring a formula of the0type dll .Considering the problem as a whole, the evidencet.0-tends to favour the first view.A co-mparison of the conditions obtaining in methyl bromoacetateand phenyl bromoacetate may serve to illustrate this interpretation.CH,B r C 40\&.MeI n the phenyl ester a greater proportion of the residual aflinityof the hydroxylic oxygen atom is absorbed by the phenyl groupthan in the case of the methyl ester, so that the attraction betweenthe oxygen atoms is lessened.A more unsaturated or, it mightbe said, a more ketonic form of carbonyl is thus produced, withconsequent increase of reactivity of the bromine atom.0A similar structure may be applied to the amides: -CHi . \N:Replacement of the amidic hydrogen atoms by groups rich inresidual affinity, such as phenyl, enhances the ketonic characterof the carbonyl group.The variations observed through the series of aliphatic estersF F 422 CLARKE : THE RELATION BETWEEN REACTIVITY ANDwhich were examined are interesting, and point to differences inresidual affinity of the several alkyl groups.The free acid is less reactive than any of the esters, whilst thereactivity increases from the methyl ester through the ethyl ester tothe isopropyl ester, that is, on successive substitution of thehydrogen atoms of the methyl group.Slator (Trans., 1905, 87,481) also has found that ethyl bromoacetate is more reactivetowards sodium thiosulphak than methyl bromoacetate. Thereactivity of the tertiary butyl ester, however, falls to a valueapproximating that of the methyl ester.On continuing substitution in a normal chain, the reactivity ofFIG. 1.Relative mass of alkyl radicle.the n-propyl ester falls to a strikingly low value, rising againslightly in the case of the n-butyl ester. Thus, both the butylesters examined display anomalous reactivity, breaking the con-tinuity of the curves.The curve furnished by the normal esters,however, perhaps displays the periodic rise and fall observed inmany of the physical properties of homologous series.It may here be mentioned that these resulta are strictly com-parable, as steric considerations can play no part in the eliminationof bromine from bromoacetic esters.The results found by Burke and Donnan (Zoc. cit.) for thereactivities of the alkyl iodides produce a curve, which, whilesimilar in appearance, leads to the opposite conclusion. ThCHEMICAL CONSTITUTION OF CERTAIN HALOGEN COMPOUNDS. 423author’s results tend to show that the residual affinity of the normalseries of alkyl groups rises from methyl to ethyl, and falls ton-propyl, rising again slightly to n-butyl.On the other hand,since the halides of groups rich in residual affinity, such as phenylor vinyl, have been shown to be distinctly sluggish towards halogeneliminating agents, it would follow from the work of Burke andDonnan that the residual affinity would be at a minimum in the ethylradicle, increasing towards methyl on the one hand, and towardsn-propyl and n-butyl on the other. A satisfactory explanationremains yet to be put forward to account for the discordant resultsFIG. 2.2402002 160 -8xc3.-G 120yoao I 20Relative VICCSS of alkyl radicle.obtained for reaction velocity measurements in so far as the alkylgroups are concerned.With regard to the variations in reactivity due to the structureof the alkyl radicles, no influence ascribable to ‘‘ alkylene” or“ akylidene ” dissociation (Nef, Annden, 1899, 309, 126) can bea t work, dissociation of this type being highly improbable incarboxylic esters.The measurements carried out with methyl bromouetate indicatethat the reaction with pyridine takes place with far greater velocityin aqueous alcohol than in absolute alcoholic solution. Slator an424 CLARKE: THE RELATION BETWEEN REACTIVITY ANDTwiss (Trans., 1909, 95, 99), on the other hand, find that sodiumthiosulphate reacts more rapidly with methyl iodide and withchloroacetone in aqueous-alcoholic solution than in pure water.In the halogen acetic acicis and their derivatives, the influencebetween the halogen atom and the carboxyl group may be regardedas mutual, since Lichty (Amer.Chiem. J., 1895, 17, 27) has shownthat the initial veIocities of esterification of chloro- and bromo-aceticacids by ethyl alcohol are greater than that of acetic acid. Lichty hasalso shown (Anmlen, 1902, 319, 369) that the initial esterificationvelocity and affinity constants of the a-halogen-fatty acids greatlyexceed those of the P- and y-halogen-fatty acids. This is in entireharmony with the decreased reactivity of the bromine in ethylP-bromopropionate as compared with ethyl bromoacetate.EXPERIMENTAL,The substances employed for the reactivity measurements werein most cases purchased from Kahlbaum, or prepared by standardmethods. Semi-normal solutions of pyridine and the varioushalogen compounds in absolute alcohol were prepared, 50 C.C.ofeach solution being mixed and maintained a t 55'6O. At definiteintervals of time, 10 C.C. were withdrawn and titrated withstandard silver nitrate (approximately N l lo), the pipettes beingstandardised for the temperature. In some cases, potassiumchromate was used as an indicator, in others, Volhard's thiocyanatemethod was employed t o determine the end-point. The 10 C.C. ofsolution were added to about 100 C.C. of cold distilled water,covered, when the substances were highly reactive, with a layer ofether to remove the unchanged halogen compounds from the actionof the silver nitrate.The following measurements were carried out in absolute alcoholicsolution ; temperature 55.6O ; initial concentration N / 4 ; t repre-sents the timeinterval in hours, Ct the, percentage decomposition,and liT the velocity-coefficient :n-Propgl Bromide.t ......0'000 16'750 19'500 21.584 24'000 c, ...... 0-00 6-80 8.00 8-80 9'80K ...... - 0-0174 0'0182 OS0179 0.0181Mean value of K=0*0179.AZZyZ Bromide.t ............ 0'000 1.000 1.333 2.333 2500 3'000Ct ........... 0.00 23'80 29.58 42-50 43-79 48.80R ............ - 1-248 i-25a 1-268 1.246 1.245Mean value of K= 1'253CHEMICAL CONSTITUTION OF CERTAIN HALOGEN COMPOUNDS. 425t c, . . . . . . . . . . . .K . ............ , . . . . . . . . . .t c, . * . . * . . . . . . .K . . . . . . . . . . . .. . . . . . . . . . . .t ...... 0'000Ct ...0'00K ... -t ...... 0-000 c, ... 0.00K ... -t ... 0'000 1.000C t , . . 0'00 20'00K... - 1.000tcz . . . . . . . . . . . .I<. . , . . . . . . . . ., . . . . . . . . . . .t . . . . . . ct ... 0.00K ...o*ooo-Benzyl Bromide.c.000 0.500 0.667 o m ieooo 1.1670'00 39.55 46'47 50.91 56-11 60.05 - 5.231 5.209 4'9i8 5-022 5.150Mean value of K=5*118.Gin?tumyl Bromide.O*OOO 0.167 0.767 1.917 3.2500'00 1.97 8-27 18'51 27'59- 0.482 0-471 0'475 0.469Mean value of K= 0 '472.Bromoacetic Acid.0'684 1.033 1.333 1'500 1.667 1.8339'00 14-60 15.40 20'00 21-60 24'000'642 0'662 0.676 0'667 0-660 0'688Mean value of K=0*666.Met li yl Bromoace t a t e.1'000 1.500 3'000 3,500 4.000 4.5000'904 0.923 0.930 0-948 0'884 0.91418-43 25.72 41-09 45.30 47-21 50-66Mean valuc of K=0*919.Et h y I BrorrLou c e t a t e .2'000 3.000 4.000 4'500 5.0001'021 1.022 1,021 1.003 0.99133'80 43'40 50.52 53-00 55.32Mean value of K= 1.004.n-Prowl Bromoacetute.0.000 1.500 2.500 3.5840'00 22'07 31.91 40'40- 0.755 0.750 0.757Mean value of K=0.752.isoPropy2 Bromoucetate.20.88 27'97 34.67 39'401.000 1'500 2.000 2.5001.055 1.030 1'060 1'010Mean value of K=l'O48.n-Butyl Bromoacetate.t ...........,... 0-000 1'333 2-000 2.500K ........ .... - 0.754 C.792 0.764Ce .... ........ 0.00 20'09 28.36 32.30Mean value of R= 0.770.5500 6.0000.988 0.98457'60 59'664.5000.74445'603-0001.05344'113.0000.77136-6426 CLARKE : THE RELATION BETWEEN REACTIVITY ANDtert.-Butyl Bronzoacetate.t .. ... . ... ... o*ooo 1'000 1.800 2.250 2.500 ct 9 .. 9 . . ... ... 0.00 19.00 29.90 34'40 36.80K . . . . . . . . . . - 0'938 0'936 0.932 0.932Mean value of K= 0 934.Phenyl Bromoacetate.t ... O*OOO 0.433 0.600 0767 0.934 1.100 1.267 1.433 1.600K ... - 1.929 1.911 1.958 1.936 1-963 1.907 1'915 1.919Mean value of K=1.927.Ct ... 0-00 17-28 22.28 27'28 31.11 34.95 37.67 41.70 43-40Ben& Bromoacetat e.t ......... 0'000 0.784 1.000 1.333 i:5arl 2.350 2.817 3.000 c, ...... o 00 18-71 22-83 28-95 32-60 46-10 47.29K ..... - 1'174 1.180 1'244 1-204 1.268 1'208 1-196Mean value of K=1.211.A Zly2 Bromloacetat e.t ... ... ... ... 0'000 0.834 2-067 3-000 ct ............ 0'00 13.79 28'36 36'36K . . . . . , . . . . . .- 0-769 0.766 0-771Mean value of K=0*768.Ethyl /3-Bromopropionate.t ...... O*OOO 5.250 21.500 24.000 27'500K...... I 0-0313 0.0258 0'0260 0'0264Ct ...... 0.00 3'94 12.20 13'50 15.35Mean value of K= 0.O277.Bromoacetd.t ............ ... 0'000 18-000 21'000 ct .. .. . . . . . . . . ... 0.00 5-21 6'02K , . , , . . . . . . . * . . . - 0'0122 0'0122Mean value of R=0*012.t . . . . . . . . , cr ......K .. ...t c, . . . . . . . . .K . . . . . . . . .. . . . . . . . *Chloroacetanaide.0.000 19.170 21'167 23'5000'00 5'09 5-76 6'14- 0'01120 0.01155 0'01113Mean value of K=0-01115.Chloroacetanilide.0-000 4'600 5'417 6.367 207500.00 2'96 3-55 3'94 12-01Rlcan value of KI-0.0264.- 0,0265 0.0274 0.0258 0.02683.7500'76541.782950016-780.027326*0006 '870.011445'33311 '220.0107024-06613'200'025CHEMICAL CONSTITUTION OF CERTAIN HALOGEN COMPOUNDS.427Bromoacef anilide.t ... .. 0.000 1-000 1.500 1.934 2-834 3.283 3.483 ct ... 0.00 27.65 36-50 41.85 52-80 56-35 57-50K ... - 1,463 1'532 1-485 1-578 1'573 1.665t ...... ... ct ......K ......1 . . . . . . . . . c; ......K ......t ct , . . . . . . .K . . . . . . . . .. . . . . . . . .a'ooo0'00-0'0000.00-o*ooo0.00 -Mean value of K= 1.533.Diphenylch,loroacetamide.10-500 12-000 14'000 15-500 185008-20 9'40 1G-60 11-80 13.400-0340 0.0346 0.0339 0.0345 0.0335Mean value of K= C-0341.Chloroacetorte.3.758 5.550 20.550 22.5006'30 8-66 26.20 27-40Mean value of K= 0'0686.o * o m 0.0683 0.0691 0.0661CMo roac e t o ph enone.5-100 11.550 15-5000.1336 0.1330 0'134614'56 27.75 34'30Mean value of K=0'1339.24-33029.350'068216'33335-450'1345Bromoac e t ophenon e.t .....0.000 0.333 0.500 0.667 0,833 1.000 1.333cl, ... 0.00 37.65 48-00 54.91 60.30 63.75 71.02K ... - '1-252 7.382 7.301 i ~ s s 7.035 7-358Mean value of K=7*269.The following two series of measurements were carried out in25 per cent. aqueous alcohol (by volume) ; temperature 55'6O; initialconcentration N / 8 :Methyl Bromacetate.t ...... 0-0000 o m 6 0-2000 0.2835 0-3667 0.4500 0.5333Ct ...... 0.00 17.60 27-20 34.40 40.00 44'80 48.80K ...... - 14-65 14:95 14-81 14.54 14'43 14-30Mean value of K=14*61.Potassizlm Bromacetate.6 ......0.0000 0*2000 0.3667 0-5333 0.7000 0-8568 1.0333Ct ...... O*OO 18-40 29-60 37-60 44.00 49.60 53'60Y ...... - 9-02 9-18 9-06 8-98 9-10 9-09Mean value of K= 9-07.The following compounds quoted in the foregoing list itre notdescribed in the literature428 REACTIVITY OF HALOGEN COMPOUNDS.Cinna?mjZ Brom.de, CHP h:CH CH,Br.-Cinnamyl alcohol wassaturated with dry hydrogen bromide a t the ordinary temperature,heated to looo for two hours to decoinpose the resulting additiveproduct, washed with dilute alkali and with water, dried, anddistilled under diminished pressure. It is an almost colourless oil,boiling a t 122-123°/10 mm., insoluble in water, and moderatelysoluble in organic solvents :0.1830 gave 0.1752 RgBr.C,H,Br requires Br = 40.62 per cent.n-Bzct yZ Bro moac e tu t e, C€12Br*C02*C,H, .-Equimolecular quan-tities of bromoacetic acid and n-butyl alcohol with a few drops ofconcentrated sulphuric acid were heated to looo for three hours,the product being washed with dilute alkali and with water, dried,.and distilled under diminished pressure.The substance is a colour-less liquid, boiling a t 78O/10 mm., and is insoluble in water, butmiscible with organic solvents; it possesses no sharp odour, thusdiffering from the other aliphatic esters examined :Br = 40.74.0.1085 gave 0.1046 AgBr. Br=41.02.C,H,,O,Br requires Br = 41-02 per cent.tert.-BizttyZ Bromoacetat e, CH2Br*C'0,*CMe3.--tert -Butyl iodidewas treated with a slight excess of dry silver bromoacetate suspendedin ether, the mixture being kept cool.After twelve hours, theethereal soliltion was filtered, and the ether distilled off, the residuebeing fractionated under diminished pressure. A yield of onlyabout 20 per cent. was obtained of a colourless liquid, boiling a t503/ 10 mm., insoluble in water, but miscible with organic solvents ;it possesses a pungent odour, similar to that of methyl bromo-acetate :0.1747 gave 0,1691 AgBr. Br=41*20.CGH,,02Br requires Br = 41-02 per cent.Benzyl Bromsoacetate, CH2Br*C02-CH2Ph.-Benzyl alcohol andbromoacetic acid were esterified in the manner described underr-butyl bromoacetate. The ester is a colourless liquid boiling at143O/10 mm., and insoluble in water, but miscible with organicsolvents; it possesses an odour similar to that of benzyl acetate;the vapour does not attack the mucous membranes a t the ordinarytemperature :0.2136 gave' 0.1746 AgBr.C,H,O,Br requires Br = 34.94 per cent.A ZZyZ Bromoac e tut e, CH2Br* C0,*CH2*CH: CH2.-A11y1 alcoholand bromoacetic acid were esterified in the manner described undern-butyl bromoacetate. The ester is a colourless liquid, boiling a tBr = 34-82VAPOUR PRESSURES OF TWO MISCIBLE SOLIDS. 42973O/10 mm.; it is insoluble in water, but miscible with organicsolvents, and possesses an extremely sharp odour :0.1693 gave 0.1790 AgBr. Br=45.05.C,H70,Br requires Br = 44-69 per cent,.Dipltenylchloroacetamide, CH,Cl*CO*NPh,. - Diphenylamine,dissolved in dry carbon tetrachloride, was treated with excess ofchloroacetyl chloride, the mixture being maintained at atmospherictemperature by immersion in cold water. The precipitated di-phenylamine hydrochloride was separated, and the carbon tetra-chloride removed from the filtrate by distillation. The residue,after being washed with water, was recrystallised from alcohol.The compound forms colourless needles, melting at 116O, and ismoderately soluble in organic solvents :0.1944 gave 0.1163 AgC1. C1= 14.80.CI4H,,ONC1 requires C1= 14.45 per cent.I n conclusion, the author desires to express his thanks toAssistant-Professor Smiles and to Dr. A. W. Stewart for friendlyinterest and valuable advice.CHEMICAL LABORATORY,UNIVEESITY COLLEGE, LONDON