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XXVI.—Researches on pelargonic acid

 

作者: M. Auguste Cahours,  

 

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

页码: 240-243

 

ISSN:1743-6893

 

年代: 1851

 

DOI:10.1039/QJ8510300240

 

出版商: RSC

 

数据来源: RSC

 

摘要:

240 XXVL-Researches on Pelargonic Acid. BY M. AUGUSTECAHOURS. (LETTER TO DR. A. w. HOFMANN.) The action of nitric acid on the essential oil of rue gives rise to several homologous acids. The first term of this series to which I have given the name Rutic acid only differs from the oil itself by containing two equivalents of oxygen more the latter stands therefore to the former in the relation of an aldehyde. The action of nitric acid however is not confined to a simple oxidation of the essential oil; according to the duration of the action (C H,) 2(C H,) 3(C H,) are successively oxidized,-pelargonic caprylic and cenanthylic acids and probably other more simple terms of the same series being formed. It is evident that in employing com- mercial acid and allowing it to act for some time on the oil several of these products are finally obtained the one predomi-nating over the others according to the duration of the reaction.Pelargonic acid being the one least known of this group and being also obtained the most plentifully from oil of rue I turned my attention to it in preference; its study has furnished me with the following results Pure pelargonic acid is colourless assuming an amber tint after a time. It boils steadily at 260*,and distils without undergoing alteration or change of colour ii the precaution be taken to perform PELARGONIC ACID. the distillation in an atmosphere of carbonic acid. The analysis of several specimens has furnished me with numbers leading to the formula CIS Hl 0,.This acid forms soluble and crystallizable salts with potassa soda and ammonia. With baryta and strontia it yields salts slightly soluble in water and soluble in boiling alcohol from which solu- tion they separate on cooling in the form of crystalline scales of nacreous appearance. The analysis of these salts led to the formulre RaO. C, Hi7 0 CaQ. C, H, 0,. If a current of hydrochloric acid gas be passed into an alcoholic solution of pelargonic acid an amber-coloured oil soon separates and floats on the surface ;this oil treated with a solution of carbonate of soda washed with pure water dried over chloride of calcium and distilled is obtained as a colourless liquid the density of which is 0.86; its boiling-point is between 216O and 218O.The analysis of this product led to the formula c22 H22 04 = (34 H 0.c, II, 0,. On ebullition with a concentrated solution of caustic potassa alcohol and pelargonic acid are reproduced. Pentachloride of phosphorus acts very violently on pelargonic acid hydrochloric acid gas being abundantly evolved ; if the experi- ment be performed in a distilling apparatus a colourless liinpid distillate is obtained which contains a large quantity of oxychloride of phosphorus ;on re-distilling this product and rejecting the portion which passes over before the temperature becomes stationary a limpid liquid is obtained as the latter portion of the distillate which is heavier than water and boils at 220°. This liquid which gives OR dense fumes when exposed to the air and has a veyy powerful odour evolves much heat when brought in contact with alcohol pelargonic ether being formed.The analysis of this product led to the formula CIS HI7 c10,* It is therefore the Chloride of PeZargyZ. Pelargonate of baryta is decomposed by dry distillation il residue of caybonate of baryta being obtained a brownish oil collecting in the receiver which solidifies on cooling. This substance when pressed between bibulous paper yields a solid product easily soluble in ether. The ethereal solution submitted to spontaneous VOL. IIIo-NO XI. R 242 M CAHOTJRS ON evaporation deposits large crystalline plates assuming a nacreous appearance on desiccation This product submitted to analysis yielded numbers coinciding with the formula c34 H34 0,.This substance is therefore PeZargone isomeric with margaric alde- hyde. Its formation is explained by the following equation 2 (BaO. C, HI 0,) = 2 (BaO. CO,) -I-C H3 0,. Pelargone is violently attacked by fuming nitric acid a nitrogenous acid being formed which is doubtless a homologue of that obtained by the similar treatment of butyrone If we assume that the action of an excess of alkaline base at a high temperature on the acids of the acetic series give rise to phenomena similar to those observed with benzoic acid or acetic acid itself we should expect to obtain by the distillation of pelargonic acid with an excess of potash-lime either the valyl of Kolbe or a compound isomeric with it; this presumption is not however confirmed by experiment.On submitting a mixture of pelargonic acid with from four to five times its weight of potash-lime to a temperature nearly approaching a dull red-heat a large quantity of gas is disengaged some volatile products are condensed and a residue of partially carbonated alkali is obtained. On passing the gas into bromine a portion is absorbed and the rest passes through unaltered. The portion absorbed by the bromine forms with this substance a very dense liquid which when treated with a very weak solution of potassa in order to remove the excess of bromine yields an amber-coloured heavy liquid consisting of three different substances; the one boils at 130° and crystallizes when the vessel containing it is immersed into powdered ice this is Dibromo-mylene C4 H Br,; the second boils at 143' to 144O and is the Dibromo-propylene C €1 Br ; the third which boils at 160° is Dibronzo-butylene C H Rr,.The first and particularly the latter of these substances are present in very small quantity corn pared to the prop ylene -compound. The liquid product of this reaction is of a complex nature the larger portion boils between 105O and 1loo; the latter portion distils at 136O. Several analyses made with different specimens of the liquid which boiled between 106O and llOo,have given me as a mean 84.9of carbon and 14% of hydrogen that is to say more hydrogen and less carbon than in olefiant gas; the idea naturally suggested itself that this liquid might be a mixture of valyl and of a hydrocarbon of the series PELARGONIC ACID.C H having a very proximate boiling-point ; some experiments however soon convinced me of the absence of valyl this liquid being violently attacked by some reagents that have no action on valyl. The vapour-density of this substance was found to be 3-98,which leads to the formula C, H, = 4 volumes of vapour. This substance therefore would appear to be a hydrocarbon homo-logous to olefiant gas mixed with a small quantity of foreign matter. When treated with bromine it evolves heat yielding a liquid having an aromatic odour. The analysis of this liquid yielded numbers leading to the formula c, HI Br;* The gas which is not acted on by bromine consists of hydrogen and another gas containing carbon which is probably marsh-gas.The deportment of pelargonic acid accordingly differs in this instance essentially from that of its homologue acetic acid; the carbo-hydrogen C16H,, which should be produced in this reaction appears to be possessed of but little stability splitting up as it does into hydrogen and marsh-gas. It is probable that all the acids of the acetic series furnish analogous results. I have convinced myself that this is the case at least with caprylic and mnanthylic acids.* I am just now studying ethalic and margaric acids with the same view.

 

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