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XXIII.—Contributions towards the history of caproic and œnanthylic acids

 

作者: J. S. Brazier,  

 

期刊: Quarterly Journal of the Chemical Society of London  (RSC Available online 1851)
卷期: Volume 3, issue 3  

页码: 210-229

 

ISSN:1743-6893

 

年代: 1851

 

DOI:10.1039/QJ8510300210

 

出版商: RSC

 

数据来源: RSC

 

摘要:

MESSRS. BRAZIER AND GOSSLETH XXlII.-Contributions towards the history of Caprob and CEnanthylic Acids. BYMESSRS.J. S. BRAZIER AND G. GOSSLETH Of the Royal College of Chemistry London. The leading notions which begin to elucidate the vast number of observations collected in the department of organic chemistry have been acquired in the careful study of a comparatively limited number of groups of analogous substances. The investigation of a series of bodies closely allied to each other in their composition and proper-ties and a comparison of their cornposition and properties im-parted to the results obtained a degree of interest which could not have been possibly claimed by the most accurate and minute exami-nation of an isolated compound. Among the groups of substances the study of which has thus most materiaIly assisted in the elaboration of our theoretical views the series of acids usually called fatty acids appears in the first rank.This series commencing with formic acid the simplest of all organic acids and terminating with an acid of so high an equivalent 88 rnelissic acid discovered by Mr. Brodie,* is at once distinguished by the definite character of its members by the extent to which it is represented by well-investigated terms and by the variety of sources belonging to almost all the various departments of organic chemistry from which these terms have been derived. Descending from the alcohols by way of the aldehydes and connected with the former group in another manner by the nitriles again related in its deriva- tives with marsh-gas and its homologues as well as with the increas- ing family of acetones the history of this group when traced in its various ramifications extends over a field on which we meet with almost all the compounds esseutially concerned in the progress cf chemical science.In the following pages we beg to communicate to the Society a few contributions towards the history of the fatty acids which not-withstanding their fragmentary nature may be acceptable on account; of the interest attached to the subject. These communications refer to the sixth and seventh term of the series of fatty acids namely caproic and ananthylie acids. CAPBOIC ACID. This acid discoyered by Chevreul in the course of his unforgotten researches into the nature of fatty bodies and subsequently met with ON CAPROIC AND (ENANTHYLIC ACID.in cocoa-nut oil by Fehling,* has been produced of late under very remarkable circumstances from cyanide of amyl by Messrs. Kolbe and Frankland.? In order to avoid the tedious processes of saponi-fication and subsequent fractional distillation of the volatile products or of separating the acids by the different solubility of their baryta- salts we resolved to prepare the acid by the latter method. In the course of this process we made one or two observations which may be mentioned. The sulphamylate of potassa used in making cyanide of amyl was prepared at once from sulphamylic acid by saturating it with crude carbonate of potassa.Nearly the whole of the excess of sulphate of potassa formed was separated during this operation the remaining portion crystallizing out by the evaporation of the solution. The perfectly dry sulphamylate of potassa when distilled with cyanide of potassium in the proportion of three to one yields cyanide of amyl. In the commencement we performed this distilla- tion on a rather considerable scale in iron retorts the irregular action of the heat however induced the formation of a large amount of secondary products; and we found it more advisable to work with smaller portions. The operation succeeds very well in Florence flasks placed obliquely upon a wire-gauze over a gas-burner. The liquid obtained in this distillation is by no means a definite compound.Its terrible odour indicates at once the presence of a considerable amount of prussic acid. When subjected to distillation it begins to boil at about lZ5OC (257O I?.) the boiling-point rising gradually to 150' C (302OF.) about which temperature a semi-solid yellowish- white mass of crystalline appearance remains behind in the retort. A similar product is deposited in the tube of the condenser. It may here at once be stated that this liquid contains in addition to cyanide of amyl a pod deal of fusel-oil and moreover a considerable quan-tity of both liquid cyanate and solid cyanurate of amyl the ti*o latter evidently arising from the presence of a large amount of cya-nate of potassa in the commercial cyanide of potassium. This sub-stance which is now manufactured in this country by hundred- weights is invariably prepared by Liebig's process the success of which as is well known actually depends upon the simultaneous for- mation of the cyanate.In the first place we attempted to purify the crude cyanide pre- viously to its conversion into caproic acid ;but after having ascertained * Ann. Ch. Pharm. LIII 390. f Ann. Ch. Pharm. LXIX 418. P2 MESSRS. BRAZIER AND GOSSLETH the nature of the impurities we at once subjected the crude product collected between 130° and 150° to the action of the alkali. The products of decomposition furnished by the cyanide and cyanate are so opposite in their chemical character-the one yielding a strong acid caproic acid the other a powerful base-amylamine or valera-mine-while the fusel-oil present remains unaltered-that the separation after decomposition follows as a matter of course whilst separation by fractional distillation before the action would have been a tedious and nevertheless imperfect operation.The conversion of the cyanide of amyl may be effected by an aqueous solution of potassa we found however that the operation succeeds much better with a solution of the alkali in alcohol. The mixture when boiled in a flask connected with a condenser in such a manner as to induce the liquid to return to the alkali readily changes into a pasty mass while torrents of ammonia are evolved. After half an hour's ebullition the mixture is introduced into a retort and subjected to distillation when a small quantity of am-monia alcohol amylamine and fusel-oil distil over a solution of caproate of potassa remaining behind which usually solidifies on cooling into a semi-crystalline mass.The distillate was mixed with some hydrochloric acid and sub- jected once more to distillation; it began to boil at about 78O C. (17ZU*4F.) the first product consisting of alcohol ;the boiling-point rose gradually to 131O C. (267O.8F.) at which temperature pure fusel- oil distilled over a syrupy mass remaining behind containing chiefly hydrochlorate of amylamine and from which an additional quantity of fusel-oil was separated by addition of water. The dilute solution when boiled for some time in order to drive off fusel-oil which was still mechanically adhering and distilled with potassa yielded a considerable quantity of pure amylamine.The production of this base under these circumstances is as we have mentioned due to the decomposition of the cyanate and cyanurate of amyl these substances as Wurt z has shown assimilating the elements of water are split up into carbonic acid and amylamine. In several operations the production of the latter base nearly equalled the quantity of caproic acid obtained which shows how much cyanate is present in many kinds of commercial cyanide of potassium. With respect to the properties of amylamine we have scarcely to add anything to Wurtz's description j however as we had a considerable quantity of the substance at our disposal we determined its boiling-point with accuracy.Amylarnine boils constantly at 93' C. (199O.4F.) We adduce moreover an analysis of the platinum- ON CAPROIC AND (ENANTHYLIC ACID. salt of this base which leaves no doubt as to its identity with amylamine. The platinum-salt being soluble in water was easily purified by one or two recrystallizations. I. 0.5722 grms. of platinum-salt gave 0.4259 , , carbonic acid and 0.2578 , , water. 11 0*6210 , , platinum-salt gave OS2077 , , platinum These numbers lead to the following percentage which we place in juxtaposition with the theoretical values of the formula C, H, N. HCI. 1%Cl,. Theory. Experiinent . 10 eqs. of Carbon . . 60-00 20.46 20.30 14.00 4-78 5-00 14 , , Hydrogen . I 1 , , Nitrogen . . f&OQ 4-78 3 , , Chlorine .. . 106.50 36.33 -) Platinum . . 1 98.68 33.65 33.45 > 1 eq. of Bichloride of Pla-293,114; loo,oo tinum and Arnylamine The solution of caproate of potassa concentrated if requisite by evaporation was gradually mixed with sulphuric acid when caproic acid separated as an oily liquid lighter than water. It was removed by a tap-funnel and subjected to rectification. The acid obtained in this manner was not perfectly pure; when submitted to distillation it was found that the thermometer rose at once to and became constant at 198O C. (388O.4F.); at which tem- perature the larger portion of the fluid distilled over ; the mercury then rose gradually to 211O C. (411O*8F.) The first fraction when rectified exhibited exactly the same boiling-point as before several ounces distilling over without any oscillation of the mercury whence we do not hesitate to consider 198O C.(388O.4F.) as the boiling- point of caproic acid Fehling'g had found that the acid obtained from cocoa-nut oil boiled at 202O C. (395O.6 F.) CAPROATE OF AMYL. We have just stated that the thermometer continued to rise after the distillation of the pure acid. The product passing over between * Anu. Ch. Pharm. LIII 390. MESSRS. BRAZIER AND GOSSLETH 200°and 2114 differed in its odour from that of caproic acid; it was found to be partly soluble in alkaline and not at all in acid liquids and formed only a comparatively small percentage of the total amount of liquid. In order to obtain a sufticient quantity of this compound for examination a considerable portion of crude caproic acid was treated with a solution of carbonate of potassa when the caproic acid was dissolved with evolution of carbonic acid an oily liquid separating on the surface of the solution.When removed with a separating funnel and dried over chloride of calcium it exhibited after rectification a constant boiling-point at 211O C. (411°*8F.) The analysis of the oily liquid gave the following results I. 0.2485 grms of substance gave 0.6410 , , carbonic acid and 0.2675 , , water. 11. 0.2075 , ,)substance gave 0.5386 , , carbonic acid and 0.2231 , , water. Percentage-composition I. 11. Carbon . 70.75 70.80 Eydrogen . 11.95 11*94 These numbers closely agree with the formula as exhibited in the following comparison of the theoretical values with the results of experiment Theory.Mean of Experiment. -22 eqs. of Carbon . . 132 70.96 70-78 22 , , Hydrogen . . 22 11.82 11.94 4 ,) , Oxygen . . + 32 17.22 -186 100.00 The formuh c22 If22 04 represents the composition of caproate of amyl Cl Hn*Cl Hl 0,. The observed boiling-point of this compound coincides pretty closely with the number calculated if we start from the boiling-point of valerate of amyl which according to I3 alard’s determination ON CAPROIC AND (ENANTHYLIC ACID. 215 is 190° C. (374OF.) The deportment of the above substance with an alcoholic solution of potassa leaves no doubt in this respect. The mixture when heated was readily converted into a gelatinous mass from which water separated pure fusel-oil while addition of sulphuric acid to the remaining alkaline solution induced the liberation of an oily acid which by analysis was proved to be caproic acid.When it was separated by distillation dissolved in ammonia and converted into a silver-salt 0*2814grms of silver-salt gave 0*1408 , ? silver = 48.65 per cent. of silver. The formula At5 Cl HI 043 requires 48-43per cent. Caproate of amyl has a very disagreeable smell and pungent taste is perfectly insoluble in water of a lower specific gravity but soluble in every proportion of alcohol and ether. The formation of caproate of amyl under the adduced circm- stances appeared at the first glance rather enigmatical.We soon found however that fusel-oil is soluble to a certain extent in a soh-tion of caproate of potassa. The separation of caproic acid by sd-phuric acid in the presence of amyl-alcohol could not fail to produce a certain quantity of the compound ether in question. ACTION OF HEAT UPON CAPROATE OF BARYTA. The members of the series CnH O, when subjected to the action of heat split as is well known into water carbonic acid and a new class of bodies known under the name of acetones or ketones according to the following equation Cn Hn 0,Z= HO + Cog + C(n-1) H(n-1) 0 lThis metamorphosis is generally effected by the distillation of the lime-or baryta-salts in which case the carbon becomes fixed in the form of a carbonate.In preparing the ketone of caproic acid we availed ourselves of the baryt a-sal t . This salt is easily prepared by means of carbonate of baryta and caproic acid; it is very soluble in water. The solution when left to evaporate in vacuo over sulphuric acid deposits crystalline plates. By ebullition the odour of caproic acid becomes perceptible and a white mass separates which can be dried without decomposition at a temperature a little above 1000C. The dry mass evidently a 216 NESSRS. BRAZIER AND GOSSLETH somewhat basic salt is brittle and may be easily powdered; for the distillation of the salt we employed small quantities at a time. At a gentle heat the salt fuses without charring in the least nearly white carbonate of baryta remaining behind ;nevertheless only a compara-tively small quantity of liquid product is obtained as distillate.Experiment showed at once that the action by no means consists exclu- sively in a separation of carbonic acid ; for during the whole process a permanent inflammable gas was evolved the quantity of which appeared to increase in some measure with the temperature at which the distillation was performed. Caproate of baryta when suddenly exposed to a rapidly rising temperature disengages this gas in con-siderable quantities only a small portion of oily products being formed which are moreover very dark and resinous whilst the distillate obtained at moderate temperatures is nearly colourless. The carbonate of baryta which remains in the retort is nearly black from separated carbon !J%ese facts as well as the observations made by Chancel and Guckelberger* in the analogous decomposition of butyric valeric and caprylic acids left no doubt that the liquid pro- duct was a mixture of various substances.When dried over chloride of calcium and subjected to distillation it commenced boiling at 120°C. (248OF.) the boiling-point rising gradually to 170°C. (338O F.) Between 160° and 170° the largest quantity was collected. This portion 011 rectification showed a pretty constant boiling-point at 165O C. (329OF.) With the lower portions no constant boiling-tem- perature could be observed. Several combustions made with this product exhibited invariably a deficiency of carbon when compared with the percentage of carbon required by the formula0 f caprone CI1H, 0.This as well as the results of Chancel who actually separated butyrale or at all events a substance of similar composition from the product of distillation of butyrate of lime lead us to believe that a small quantity of caprale CIz H, 0, may be formed in this process. This assumption is supported by the deportment of the lower dis- tillate from which ammonia removes a small portion of matter. The ammoniacal solution after having been exposed to the air for some time yields with acids oily globules having the characteristics of caproic acid. Unfortunately we had not enough material to elabo- rate this question any further. We were however benefitted by the observation inasmuch as it induced us to submit the chief fraction boiling at about 165O previously to analysis to an addi- * Ann.Ch. Pharm. LXIX 20. ON CAPROIC AND CENANTHYLIC ACID. tional distillation over hydrate of potassa. After this treatment it showed a constant-boiling point at 165O C. (329OF.). When burnt with protoxide of copper this liquid gave the following results I. 0.1641 grms. of substance gave 0.4655 , , carbonic acid and 0.1949 , , water. If. 0.2263 , , substance gave 0.6423 ,) , carbonic acid and 0.2668 , ) water. Percentage-composition 1. 11. Carbon . . 77.36 77.42 Hydrogen . . . 13.18 13.10 These numbers closely correspond with the formula Cll H1,0 as may be seen from the following table Theory. Mean of Experiment.11 eqs. of Carbon 66 77'64 77.39 11 , Hydrogen 11 12-94 13-14 1J 1) Oxygen 08 9-42 -I eq. tt Caprone . 85 100*00 Caprone is a very mobile liquid insoluble in water to which however it imparts its peculiar oiour-; it is readily soluble in alcohol and ether. After being distilled from potassa it is perfectly colourless but rapidly turns brown when in contact with the atmosphere pro- bably in consequence of oxidation. Its boiling-point is 165O C. (329OF.),and its specific gravity is lower than that of water. These results show that one phase of the action of heat upon caproate of baryta may be represented by the equation Ba. C, HIl 0,= Ba. CO i-C, H, 0. We say one phase because a series of other metamorphoses is pro-ceeding smultaneously with the conversion of a portion of the acid into caprone.The amount of this substance obtained is quite out of pro-portion with the quantity of baryta-salt employed. We have men-tioned that we have reason to believe that the aldehyde of caproic acid is simultaneously formed and alluded to the large quantity of permanent gas disengaged. This gas consists chiefly of hydrocar-bons and probably contains a similar mixture of the hydrocarbons 218 MESSRS BRAZIER AND GOSSLETH C H, which Dr. Hofmann observed in the distillation of valerianic acid.* The preparation of caprone adds another member to the group of ketones running parallel with the series of fatty acids. This group first announced in the formation oi" acetone which may be still con-sidered as its prototype and subsequently illustrated by Chancel's researches into the derivatives of butyric and valeric acids embraces at this moment the following members which we give in juxtaposi-tion with their mother-acids Acetic acid .. C €3 0,;C H 0 Acetone; Liebig & Dumas Propionic acid. Propioue ; Metacetic acid. O'{ Metacetone; FrBmy. } . C '6 '6 '4; '5 H5 Butyric acid Hs 0,;C H 0 Butyrone; Chancel. Valeric acid . . C, HI*0,;C H 0 Valerone; Chancel. Caproic acid . . C, H, 0,; C, HI 0 Caprone ; G. & B. Caprylic acid . c16 0,; C, H, 0 Caprylone; Guckel-berger. C, H, 0,;C, H, 0 Margarone ;Bussy. Margaric acid . This table shows that the ketone of formic acid is still wanting; the series then regularly ascends up to cmanthylic acid whose deri- vative has not yet been prepared; we perceive moreover that a wide gap occurs between caprylic and margaric acid the filling up of which will require some time and labour.It deserves to be men- tioned that one of the terms which we have inserted in the above table has not hitherto been obtained from the collateral acid. Propione (metacetone) originally prepared by Prkm y by distilling sugar starch orgum with lime has been represented by its discoverer by the formula c6 H 0; it is probable however that Fre'my's substance contains one equiv. of carbon less. Its properties coincide in almost every respect with propione as pointed out by theory. Acetone and its congeners have been of late the subject of some interesting speculations on the part of M.Chance1.t The formula which we have given in the above table represents 2 volumes of vapour and this is the mode of condensation adopted by the majority of chemists. M. Chancel on the other hand is of opinion that the ketones like the hydrocarbons contain 4 vols. of vapour he doubles * The chief component of this gas is as I have stated propylene. I have since learnt from M. Cahours that pelargonic caprylic and cenanthylic acids likewise yield this hydrocarbon in preponderating quantities so that we may fairly assume that caproic acid exhibits a similar deportment.-A. W. H. -$-J. Pharm. [3] XIII,468. ON CAPROIC AND GNANTHYLIC ACID. 219 the formulze and considers these substances as formed by the intimate combination of 1 equivalent of the aldehyde of the acid with 1equi-valent of the hydrocarbon belonging to the group which is placed a step lower on the ladder of organic substances.According to this view acetone is not represented by c H 0 but by C H6 0,= C4 H4 0,+ C H:,; i. e. it has to be considered as a combination of the aldehyde (par eweZZence) and methylene consequently the ketones would always arise from the decomposition of 2 eqs. of the respective acids 2 Cn Nn 0,=2 HO + 2 CO + C H 0%+ Cln-2) The following table into which we introduce the boiling-points which have been observed exhibits the various ketones when viewed in this light Boiling-point. Acetone . C H O:,=C €I4 0,+C2 H:,..56OC. (13Zoo8F.) Propione .C, H, O,=C H6 O,+C H .. 84' C (183O*2F.) Butyrone . C14 HI4 O,=C H 02+C6 N . . 144O C. (291'3 F.) Valerone . C, H, 0,=C1 H, O,+C H Caprone C, H, 02=C12 H, 02+C, HI,. . 165' C. (329O.OF.) Caprylone. C30 Hs0 02=C16 H16 02+C, H,,,. . 178O C (352O*4F.) Margarone C Ha6 o,=c34 H, 02 +C3 H3 Chancel's view is chiefly supported by the deportment of some of the ketones under the influence of oxidizing agents. In fact acetone when boiled with chromic acid yields a mixture of acetic and formic acids the former being (in the conception of this theory) derived from the aldehyde while the latter is due to the presence of a term belonging to the lower series If acetone were C H 0,this conver- sion would be almost unintelligible.In the same manner propione is converted into propionic and acetic acids By treating butyrone with nitric acid C hancel* obtains nitropropionic acid which may have been formed by the oxidation of the propylene; Chancel gives no account of what becomes of the other term the butaldehyde occurring in his formula. On the other hand we find that the formation of butyrone is invariably attended by a simultaneous production of butal-dehyde (butyrale) which may be due to a partial decomposition of the butyrone in the nascent state probably with evolution of propylene. The generation of valerone and as we have seen of caprone gives rise * J. Pharm. [S] XIII 463. 220 MESSRS. BRAZIER AND GOSSLETH to similar phenomena. It remained now to study the deportment of the latter compound under the influence of oxidizing agents.ACTION OF NITRIC ACID UPON CAPRONE This body mas very readily attacked by nitric acid. If strong acid was employed oxidation ensued without the application of heat as soon as the evolution of nitrous fumes had ceased the liquid in the retort was saturated with carbonate of potassa when an oily liquid of a peculiar aromatic odour separated which was insoluble in an excess of the alkaline liquid. The quantity at our disposal was so very small as to preclude altogether the possibility of a closer examina- tion. The alkaline solution separated from the oil by ebullition was now acidified with sulphuric acid and subjected to distillation when an acid liquid was obtained upon which a small quantity of an acid oil was floating.When saturated with ammonia and precipitated with nitrate of silver a white crystalline silver-salt was obtained. The quantity of material at our disposal was just sufficient for a silver-determination 0,4566 grms of silver-salt gave 0*1088 ,9 ,,silver. Percentage of silver 42.29 This number although somewhat low would indicate that tbe salt analysed was nitrovalerate of silver ; the slight deflagration which occurred on igniting the salt gives further evidence in favour of this view The formula requires 42.5 of silver. If the acid formed by the action of nitric acid upon caprone be actually nitrovaleric acid-which has to be proved by additional experimental evidence-the deportment of this ketone would be per- fectly analogous to that of butyrone which yields nitropropionic acid.In both cases we may ask what becomes of the aldehydes which accordins to the analogy of the lonw terms should be con- verted into their correlative acids namely into caproic and butyric acids. These acids which according to Chancel’s formula should be formed in quantities equal to those of uitrovalerk and nitropro- pionic acid and which should be produced even more readily than the latter acids have not as yet been observed in the respective pro- cesses Hence it appears that many further researches are requisite ON CAPROIC AND CENANTHYLIC ACID. 221 in order to establish Chancel’s interesting speculations. The chief difficulty which we meet in the study of’ the higher terms of this series is the great amount of acid required the preparation of which is both laborious and expensive.Before leaving this question we may still take a glance at the boiling-point of the substance under consideration. The difference of the boiling-point of acetone and butyrone 144O-56O =88 = 4x 22 agrees very well with C hancel’s view ;the boiling-point of propione is stated at 84O instead of loou which would be the temperature assigned by theory. However as propione has never been prepared from propionic acid we can scarcely place implicit reliance upon the statements at present in our possession; it is possible that the pro-duct investigated produced as it was in an irregular process of destructive distillation still contained some of the substances simul- taneously generated acetone &c.The boiling-points of caprone and caprylone (Guckelbefger) are not at all favourable to Chancel’s assumptiml. Caprone boiling at 165’ (3. (329OgOF.) should according to theory boil as high as 232O C. (499O.6 F.) ; caprylone the theoretical boiling-point of which is 320° has been found to enter into ebullition at as low a tem-perature as 178O C. (352O-4F.). We have however to bear in mind that the present state of our knowledge respecting boiling-points is very deficient; the empirical rule at which we have arrived holds good only for a certain range of the thermometer the difference of the boiling-temperatures increasing towards the lower and decreasing towards the upper liiizit.We have to apologize for the unsatisfactory state in which we are obligcd to leave this question for the present we say for the pre- sent because it is our intention to return to this subject as soon as possible. We hope more especially soon to obtain additional data respecting the composition and tbe properties of nitrovaleric acid. The deportment of this acid under the influence of reducing agents promises interesting results; for should this acid -as we have every reason to believe-imitate the behaviour of nitrobenzoic acid,* its analogue in the benzoyl-series it will put us in possession of carbobutylic acid from which a single step downward would lead to butylaniine. * Benzoic acid . . C, €1 0,. Valerie acid . . . .C, W, 0,. Nitrobenzoic acid . C14{ 20,}04. NitrovaIeric acid . Clo{ zb4}0,. Carbanilic acid . . C, EH2 0,. Carbobutylic acid . . . C.{ ?H,} 0,. i51 Aniline CI2 H,. N Butylamine (Petinine) C HI1 N 222 MESSRS. BRAZIER AND GOSSLETH DECOMPOSITION OF CAPEOIC ACID UNDER THE INlLUENCE OP THE GALVANIC CURRENT. Among the various derivatives of the series C H 0, few have created more interest than the substances which Dr. Kolbe* has obtained in the electrolysis of acetic butyric and valeric acids. In subjecting the potassa-salts of these acids to the current he formed among other products the compounds Methyl w% Propyl C,H Butyl (Valyl) . C H which he considers as the radicals of methylic propylic and butylic (valylic) alcohols.Several analogous substances such as ethyl and amyl having lately been obtained by Dr. Frankland? in a totally different mode of decomposition from actual alcohol-compounds it appeared of some interest to extend the galvanic process to a case which would yield a product previously formed by the chemical method. For this purpose we have studied the action of the pile upon caproic acid whose decomposition promised to furnish the compound amyl C1 Hllr previously obtained by Dr. Frankland$ from iodide of amyl. The apparatus used in the decomposition of caproate of potassa prepared from pure caproic acid boiling at 1984 was perfectly similar to that minutely described in Dr. Kolbe's memoir. When six of Bun sen's zinco-carbon elements were employed the decompo- sition of the concentrated solution of caproate of potassa succeeded without difficulty.The liquid rapidly assumed a milky appearance from the separation of numerous gas bubbles and small oily droplets which gradually collected as a layer of oil upon the surface of the liquid contained in the decomposition-apparatus. The gases disengaged consisted chiefly of carbonic acid and hydrogen mixed however with it compound imparting to them a peculiar aromatic odour. The oily liquid when separated by means of zb pipette and sub- jected to distillation began to boil between l25O C. (257O F.) and 160'C. (320' F.) It was evident that as was the case in the corre- sponding decomposition of valeric acid this liquid consisted of a variety of products.Only a limited quantity being at our disposal we at once resorted to the process of purification pointed out by Dr. Kolbe. * Chem. SOC. Mem.111,318. $ Chem. SOC.&ti. 3. 111 262 $ Chem,SOC. &a. J.I11,30. ON CAPROTC AND CENANTHYLTC ACID. For this purpose the liquid was distilled with an alcoholic solution of potassa when a potassa-salt remained in the retort which on addition of a mineral acid yielded an oily acid Although we have not made an analysis of this substance we have no doubt that it was caproic acid; we may here adduce the analogous formation of the acids both in the Valerie as stated by Dr. Kolbe and in the cenanthylic series as proved by our own experiments detailed hereafter. The alcoholic distillate yielded with water a light aromatic liquid which was separated by a tap-funnel and dried over chloride of cal-cium.When subjected to ebullition it commenced boiling at 150° C. (302OF.) the boiling-point becoming stationary at 155O C. (311OF.) when a fraction was collected separately. At 160°C. (320OF.) every drop had passed over. The liquid distilling at 155O possessed all the properties assigned by Frankland to the compound obtained in thed decomposition of iodide of amyl by metallic zinc. When subjected to combustion with prot-oxide of copper the fol-lowing numbers were obtained I. 0.1996 grms. of substance gave 0.6171 , , carbonic acid,* 11. 0.2130 , , substance gave 0.6579 , , carbonic acid and 0.3010 ,) )) water.Percentage-composition I. 11. Carbon Hydrogen . . 84-32- 84.23 15.10 These numbers correspond closely with the formulae c,,HI Or (320 H221 as may be seen from the following comparison The0ry. Mean of Experiment -lOeqs of Carbon . . 60 8450 84.26 a 11. , , Hydrogen 11 15.50 15*70 1 eq. , Amy1 . . 71 100.00 99.96 These results leave no doubt that the substances obtained in the electrolysis of caproic acid and in the decomposition of iodide of * Hydrogen lost 224 MESSRS. BRAZIER AND GOSSLETH amyl are identical ;and hence we may assume generally that the action of zinc upon an alcohol-iodide (C I,) arid the electro- lysis of an acid C(n+ztH(n+z)0, give rise to the formation of the same compound. The products collected above and below amyl contain other products besides amyl; but we are not at present in posses-sion of suiiicient data to form a correct idea respecting the na-ture of these substances.From the analogous observations of Dr. Kolbe in the valeric series we should expect to meet in the lower fraction the hydrocarbon C, H, and fusel-oil arising from the decomposition of the compound ether C, Hll. C, HII 0 by the contact of the crude oil with potassa. We have not as yet studied this question with sufficient accuracy; but it may be even now stated that in the lower fraction we have not up to the present moment been able to detect fusel-oil. Moreover the existence of an ether C, Hll. C, H, 0, in the crude product of the electrolysis ,is not supported by the results of observation for this compound ether which would be nothing else than the caproate of amyl prepared by us as stated above boils at 211O C.(411°%F.) whilst the crudc product entirely distilled below 180°C. (356O F.) However we leave this question open and are satisfied to have established by experi- ment the analogy of the principal metamorphosis of valeric and cnproic acids under the influence of the galvanic current. DECOMPOSITION OF CENANTHYLIC ACID UNDER THE INFLUENCE OF THE GALVANIC CURRENT. Incidentally to the experiment with caproic acid we have also subjected cenanthylic acid to the action of the pile. The acid which served us for the experiments communicated in the remaining portion of our paper was prepared in the manner recommended by Tilley,* by acting upon the oil of Ricinus corn-rnunis with dilute nitric acid.By this means with considerable patience a sufficient amount was obtaiued. We have tried various other processes oxidation of the oil with chromic acid or a mixture of bichromate of potassa with sulphuric acid or treatment of ananthale with various oxidizing agents ; but we have invariably found that the action of nitric acid on the oil although tedious in the extreme still gives the best results. The crude acid was repeatedly washed and afterwards redistilled with water in order to ensure its perfect purity. As it is partially decomposed by distillation alone * Cbem .Soc.Mem. I. O?$ CAPROIC AND CEXANTHYLIC ACID. we tested its purity by the analysis of a silver-salt in preference to taking th e boiling-point.0.2324 grms. of silver-salt gave 0*1052 , , silver yielding a percentage of 45.30 of eilver. Theory requires 45.56 of silver. The potassa-salt was easily made by neutralizing the acid with pure carbonate of potassa. This salt is not crystallizable; it is easily soluble in water. The phenomena observed in the decomposition of aenanthylic acid are perfectly analogous to those exhibited in the electrolysis of caproic and valeric acid,-evolution of carbonic acid and hydrogen sepa-ration of an oily layer in the decomposing apparatus and formation of carbonate and bicarbonate of potassa in the residuary aqueous solution. The oily layer which had an ethereal odour and a sweetish taste was separated dried and subjected to distillatioii.]It boiled between 230° (266OF.) and 230° (446OF.) the thermometer exhi- biting a tendency to become stationary towards 190° (374O F.) Near the close of the operation the liquid assumed a dark-brown colour and a considerable quantity of charcoal remained in the retort. The separation of the various constituents of the oil was effected by treat-ment with an alcoholic solution of potassa exactly as in the product obtained from caproic acid. However as we performed these experiments upon a somewhat larger scale we took care to establish by analysis the nature of the acid remaining in form of a potassa-salt. For this purpose the acid was separated by hydrochloric acid washed converted into the ammonia-salt and subsequently into the silver-salt.0.4965 grm. of silver-salt gave 0-2260 , , silver == 45.51 per cent Theory requires 45.56 per cent. These numbers establish beyond doubt the separation of anan-thylic acid by potassa from the crude-oil product. The alcoholic distillate when treated with water yielded an oily liquid which after being dried with chloride of calcium boiled between 170° (338O F.) and 210° (410° F.) ; by far the largest quantity how-ever distilled at 202O (395*6Ol!.) In fact the thermometer became stationary at this temperature even in the first rectification. The fraction collected round this point n hen distilled once more exhi-VOL. III.-~O. XI. a MESSRS* BRAZIER AND GOSSLETH bited a perfectly constant boiling-point at 20.2' (395.6 F-) This liquid had a very agreeable aromatic odour it was insoluble in water but miscible in all proportions with alcohol and ether Analysis gave the following results I.0.2245 grins. of substance gave 0.6940 , , carbonic acid and 0.3160 , , water. 11 0.3345 , , substance gave 1.0370 , , carbonic acid and 0*4650 , , water. Percentage-composition I. 11 Carbon . . 84.49 8454 Hydrogen . . 15.60 15*44 These numbers correspond closely with the formulze clz HH13 Or c24 H26 as may be seen from the following comparison Theory. Mean of experiment. -12 eqs. of Carbon * . 72 84-70 84.52 13 , , Hydrogen 13 15.30 15.52 1 ,* , Caproyl . . 85 100.00 The formula C, HIS,homologous to those of methyl ethyl &c.would represent the radical of an alcohol C, H, 0, standing to caproic acid in the same relation as acetic acid stands to wine- alcohol. This alcohol might be termed caproylic alcohol and the corresponding radical hydrocarbon caproyl. The nomenclature of this series is so sadly embarrassed by the accdmulation of similar names in the eighth and tenth family that-objectionable though the rechristening of chemical compounds may be-we believe that the suggestion of more appropriate names for caprylic and capric acids would meet the general approbation of chemists. It would have given us much pleasure to have studied the deport- ment of caproyl under the influence of re-agents the more so as the pinions of chemists are divided respecting the formuk of the so-called radicals some of them adopting expressions corresponding to 2 volumes of vapour others preferring 4 volumes in a formulz.The study of the products of decomposition of caproyl might have decided this question ; bnt unfortunately the limited quantity of substance at our chsposal ON CAPROIC AND (ENANTHYLIC ACID prevented us from following out this direction of the enquiry. Moreover caproyl exhibits but little disposition to furnish readily accessible products,* We mention only that the substance is not affected by concentrated sulphuric acid and that it may be distilled with moderately coneen- trated iiitric acid without undergoing any change It was only by distillation with a mixture of the two acids that a very slow and evcn then incomplete oxidation took place.After repeated dis-tillation the distillate was mixed with water ;the supernatant oil separated by a pipette and heated with ammonia dissolved but partially. The amnioniacal solution contained an oily acid which separated on addition of a miiieral acid and exhibited the odour of caproic acid. We converted the remaining solution after boiling off the excess of ammonia into a silver-salt which was deposited as a whitish very difficultly soluble powder. After recrystallization it was obtained in slightly yellow crystals which gave on analysis the following results I. 0-2145grm. of silver-salt. gave 0.1055 , ,,silver. A second specimen prepared in a similar manner was analysed in the same way; during ignition a slight deflagration took place.11. 0.1486 grrn of silver-salt gave 0*(3686 ) ),silver Percentage 1. 11. Silver . . 4913 46.16 The theoretical percentage of silver in the caproate is 48.65 and in the nitrocaproate 40.30; the first analysis exhibits a slight excess which may be clue to reduction of a small quantity of silver during the recrystallization of this rather difficultly soluble salt. The deficiency of the secoud may possibly be owing to the presence of a * The remarkable unalterability of the so-called radicals when contrasted with the want of stability of the higher homologues of marsh-gas-as indicated by the non-production of these substances in the reaction of alkaline earths upon the higher terms of the series C H 0,-appear to discountenance more and more the assumptions of the identity of the two classes of compounds.As I had an opportunity of suggesting at an earlier period (Chem. SOC. Qu. J. 111 133) the radicals may be only isomeric bith the marsh-gas series. This of course does not interfere in the slighest degree vith the adoption of 4 volume formulze; nor does the conversion of coproyl into caproic acid which 1 consider established by the experiments of hlessrs. Brazier and Gossleth in my opinion militate in the slightest degree against the admission of the higher forinula+-A. W. H. QfL MESSRS. BRAZIElt ASD GOSSLETH small quantity of nitrocaproic acid a supposition which is supported by thc slight defiagration during combustion and by an analogous observation of Dr.I<olbe,* in the oxidation of butyl. We are sorry that our results are not more definite but hope their insufficiency will be excused by the difficulty attending these operations. We have no doubt in our own miads that the acid produced under these circumstances is caproic acid. Bromine has scarcely any action upon caproyl not even under solar irradiation. Chlorine acts very powerfulIy even in diffused day-light torrents of hydrochloric acid being immediate!p disengaged. The caproyl is rapidly converted into a viscous mass which being decomposcd on ebullition with evolution of hydrochloric acid and deposition of carbon codd not be purified for analysis. Even by a very moderate action of chlorine me did not succeed in obtaining a direct compound of caproyl with chlorine.In conclusioa we have to add thnt we have made 8few experiments with tlic oil which pasesd over before caproyl in the rectification of the liquid separated from the alcoholic distillate after treatment with potassa. This substance which has an aromatic odour and sweet taste was several times redistilled &hen a compound mas obtained boiling pretty constantly at 175O (347' F.) Analysis with protoxide of cop- per gave the following results 0.3220 grm. of substance gave 1*0070 ?, ,,carbonic acid and 0.4225 , water Percentage-composition. Theoretical values of C H,. Carbon . . 85.29 Carbon . . . 85.72 Hydrogen 14-57 Hydrogen . 14.28 These numbers show that the liquid in question is a hydrocarbon of the family C H, the slight deficiency in the carbon and the excess in the hydrogen being evidently due to the presence of a trifling quantity of caproyl We have no direct data for the value of n ;the boiling-tempera- ture would point to the formula C We have not met among the products obtained in the electrolysis of cenanthylic acid with the hydrocarbon caproylene (oleylene) C, 1Il2 or with caproylic alcohol the formation of which substance we might have expected from the analogous deportment of valeric * Chem SOC.Qu. J. 11 163 ON CAPICOIC AND CENANTHYLIC ACID. acid; we cannot however adduce any positive evidence as to the absence of small quantities of these substances.The question what compound in the crude oil gives rise to the formation of the Enan-thylic acid whether it be a kind of compound ether or an aldehyde &c. has still to be answered by furthcr experiments. One point however appears to be fixed by the preceding expe- riments namely that the members of the series C Hn 0, when treated with the galvanic current invariably give rise to the forma- tion of a hydrocarbon closely connected with the series following one step lower on the scale of organic compounds hydrosen and carbonic acid being simultaneously eiiininated. Generally expressed this metamorphosis would be represeated by the following equation C Hn 0,+ HO = Cfn-2) H(n-1) + HO + 2 CO + He This equation shows that formic acid when esposeil to the current can yield only hydrogen and carbonic acid.Together with this prin- cipal metamorphosis several secondary changes appear also to occur whose nature however is not yet perfectly understood. It deserves moreover to be noticed that these lattcr changes far from presenting the constant character of the chief decomposition appear to vary with the position of the eubstances examined upon the ladder of combustion.

 

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