FLESH OF THE CETACEAo XXV,-Researches on the Volatile Organic Bases. BY DR.A. W. HOFMANN. VIII ON THE BEHAVIOUR OF ANILINE AND THE ALCOHOL-BASES WITH NITROUS ACID.* Chemists are acquainted with the happy idea which led Piria? to examine the deportment of substances derived from ammonia under the influence of nitrous acid. The property possessed by nitrous acid of being reduced by ammonia with evolution of nitrogen ap- peared likely to afford a simple method of effecting a regular oxida- tion of the derivatives of ammonia or in other words of reconverting an amide into an oxide. N H3 + NO = 2N + 3H0, N H,X + NO = 2 N + 2 HO + XO Piria has proved by experiment that oxamide suceinamide and butyramide when treated with nitrous acid are readily reconverted into the corresponding acids nitrogen being evolved.He succeeded moreover by the aid of this process in establishing the true character of two substances asparagine and aspartic acid which have henceforth to be considered as malamide and malamic acid. At a later period the same reaction was applied to several nitroge- nous compounds of uncertain constitution by M. Strecker.f This chemist found that hippuric acid glycocine and leuciiie when treated with nitrous acid exhibit a perfectly analogous deportment the former yielding an acid C, H O, the two latter terms of avery remarkable series of acids C H O, parallel as it would appear with the series of fatty acids. * The former papers belonging to this series have been published. Chem. SOC.Qu. J. I 159 269 285; 11 36 300. t Ann. Chim. Phys. [S] XXII 160. $ Ann Ch. Pharm. LXVIII 55. 232 DR. HOP’MANN ON THE Among the various clasw of nitrogenous substances there is pcrhaps none which is likely to derive more benefit from this reaction than the group of organic bases. Connected as these substances arc with ammonia by ties of greater or less intimacy the observation of their deportment under the influence of this agent opens a field of investigation which up to the present moment has scarcely been entered upon. The only base hitherto investigated in this direction is aniline. Some experiments on the behaviour of this alkaloid have been corn-municated by Mr. T. s. Hunt,* who found that this substance when exposed to the action of nitrous acid is converted into phenole nitrogen being evolved.-N H (GI H,) + NO = C, H 0. HO + HO + 2 N. v Aniline. Phenole. This decomposition is quite in accordance both with the results obtained in the metamorphosis of other substances by Piria and Strecker and with the close relation existing between aniline and phenole-a relation which has been remarkably illustrated by the study of the derivatives of the two substances. Aniline when treated with nitric acid yields trinitrophenole whilst chlorine gives rise to the formation of trichlorophenole ; both aniline and phenole when subjected to the action of chlorate of potasea and hydrochloric acid are converted into chlorokinone (chloranile) . Experiment moreover has shown that phenole may actually be converted into aniline by exposure to the influence of ammonia at high temperatures.The position therefore of aniline as a member of the phenyl-group scarcely required the additional support of its reconversion into phenole. Still experimentally this conversion offers con-siderable interest inasmuch as it shows that this siniple process admits of eliminating the nitrogen from compounds which are capable of resisting the most powerful agents at our disposal. It is well known that the vapour of aniline may be passed over ignited soda- lime without undergoing decomposition and that we are consequently obliged to introduce certain modificationst into the ordinary process for the determination of nitrogen. The interest of the subject and moreover the fact of Mr.Hunt’s investigation being entirely qualitative induced rne to repeat his experiment with the view of proving the relation existing between aniline and phenole by definite numbers. * Sill. Am. S.Nov. 1849. * Chem. SOC.Qu. J. I 159. VOLATILE ORGANIC BASES. Mr. Hunt has performed the experiment in two different ways namely 1. By exposing a mixture of the base with nitric acid of a given strength to the action of binoxide of nitrogen as originally proposed by Piria.-Z. By acting upon hydrochlorate of aniline with solution of nitrite of silver. He obtained by both methods a dark-brown oil soluble in potassa possessing the odour of castoreum and an acrid taste and yielding with nitric acid nitrophenisic acid (trinitro- phenole) .By following the former of the two processes adopting exactIy the circumstances and proportions indicated I never succeeded in ob- taining a substance from aniline which I could with certainty have declared to be phenole. Invariably a dark-brown resinous mass was formed which indeed had the odour of castoreum and was soluble in a great excess of potassa but from which no phenole in a state of purity could be obtained. Nor was the experiment attended with better results when the circumstances mere slightly modified by substituting a weaker or a stronger acid I found that either no action at all took place or the metamorphosis went too far the aniline being converted into the brownish resinous mass. This mass may contain traces of phenole but it consists chiefly of a brown uncrystallizable substance together with a crystalline compound of most remarkable beauty which I subsequently obtained in larger quantity when acting upon aniline with a mixture of nitric and arsenious acid from which I had anti- cipated a result analogous to that obtained by Mr.Millon in the preparation of chlorous acid. This substance is nitrophenole which may be likewise obtained by acting with dilute nitric acid upon phenole itself. The study of' this compound which furnishes several links of connection between the phenole-family and various other groups will be the subject of another communication to the So. ciety. The presence of free nitric acid interfering sadly with the conversion of aniline into normal phenole yielding as it does according to the concentration of the acid products derived from this compound by a more or less advanced substitution ; I availed myself of the second process namely decomposition of the hydrochlorate of aniline with nitrite of silver.This experiment yielded a totally different result. As soon as the two substances come into contact torrents of pure nitrogen gas are evolved the whole liquid becomes turbid from the 234 DR HOFMANN ON THE separation of oily globules which are likewise of a very dark colour from which however pure yhenole may be prepared without much difficulty. When separated from the liquid by means of ether and subjected after the removal of the ether by evaporation to distillation with water they yield a quantity of a perfectly colourless oil ; but even in this process a considerable portion of resinous substances is pro-duced The oil separated from the water and rectified over an-hydrous phosphoric acid passed over in the form of a limpid liquid which solidified after a short time into a mass of white crystals possessing all the properties of phenole Analysis with protoxide of copper gave the following results 0*3080grms.of crystal gave 0.8605 , , carbonic acid and 0*1780 , , water. These numbers lead to the percentage which I subjoin to the values required by the formula c, H 025 Theory. Experiment. * 1.2 equivs of Carbon . 72 76.50 76.22 6 , , Hydrogen 6 6.38 6.38 2 )t Oxygen 16 17-02 --I_____ I 39 , Phenole .. 94 100.00 These numbers leave no doubt respecting the transformation of aniline into phenole by the action of nitrous acid. The method of employing the nitrous acid in form of a silver-salt or as I have invariably done in subsequent experiments in the form of a potassa-salt,* eliminates in a happy manner the difficulties attending the use of so powerful an agent as nitric acid under whose influence agreat many substances would uudergo further transformations. The conversion of aniline into phenole by this method renders it probable that the derivatives of aniline the anilides will admit of similar transformations. The action of nitrous acid would thus afford a general passage from the anilides to the phenides.Carbanilic acid would in this manner yield salicylic acid (carbophe- nylic acid) oxanilic acid might be converted into phtalic acid (oxaphenylic acid) relations of these acids with the aniline-series * The crude nitrite containing free potassa together with undecomposed uitrate as obtained by decomposing nitre may be employed with perfect success. VOLATILE ORGANIC BABEEL being undeniable the former passing into aniline through phenole the latter through benzole. C, H N + NO3 = C1 H6 0,4-HO + 2N U + Aniline. Phenole. C14 H N 0 + NO = C14H 06 + HO $. 2N -Y---J + Carbanilic acid. Salicylic acid. C, H N 0,+ NO = c16 H 0 + HO + 2N, + + Oxanilic acid. Phtalic acid. Whether the anilides are actually affected by nitrous acid and whether if such be the case the products formed are identical or isomeric with the substances which theory appears to suggest has to be decided by further experiments.The facility with which aniline is converted into phenole standing to it in the position of an alcohol induced me to perform some corresponding experiments with the bases of the series C H (n+3) N. This series attracted my attention particularly since it is at present much more complete than the series of collateral alcohols C 0 as seen from the following conspectus Methylic alcohol . C H 0 Methylamine C H N Ethylic alcohol C H 0 Ethylamine C H N. Propylic alcohol ? Propylamine . . C €1 N. Butylic alcohol . ? Butylamine . . C H, N. Amylic alcohol .C, H, 0 Aniylamine . C, Hi3 N. Whilst methylamine ethylamine and amylamine have been formed with the assistance of the alcohols themselves propylamine (cenylamine metacetamine) and butylamine (petinine) have been derived from sources perfectly unconnected with alcohols the former being produced according to W ertheim,* from narcotine by the action of alkalies whilst the latter was found by Anderson? amongst the products of distillation of animal substances. A deport-ment of this series with nitrous acid analogous to that exhibited by aniline would have put us in the possession of the missing alcohols. The change which these substances undergo is not perfectly similar to that of aniline. The first experiments which I performed were made with ethylamine.On distilling a mixture of hydrochlorate of ethylamine with either nitrite of silver or nitrite of potassa a violent effervescence of nitrogen took place and an aqueous liquid * Ann. Ch. Pharm. LXXIII 208. -f Phi& Mag.[3] XXXIII,174. DR HOPMANN ON THE passed over which contained no alcohol or mere trcces of it whilst a yellowish oil of a penetrating aramatic odour and a sweet but pun- gent taste floated on thc surface. The amount of this oily liquid- which had rather a higli boiling-point-being quite out of proportion with the quantity of ethylamine employed I was led to subject the gas evolved to a closer examination. I found that this gas was inflammable burning with the green- edged flame of nitrous ether that it dissolved partly in water yielding a solution in which the presence of nitrous acid could be ascertained by sulphuric acid and green vitriol aid from which the gas could be expelled again by heat.The experiment being pcr-formed during hot weather I endeavoured to condense the ether by passing the disengaged gas through a glass serpentine placed in a frigorific mixture I did not succeed however in collecting the liquid ether. This compound is diffused in so bulky a volume of nitrogen that its condensation would require both the employment of a larger quantity of ethylamine than 1 had at my disposal and the use of more efficient refrigeration and perhaps even preliminary absorption of the ether-compound in alcohol. However be this as it may the action of nitrous acid upon ethylamine gives rise to the formation of a cortsiderable quantity of nitrous ether other sub- stances being formed at the saine time.The conversion of ethylamine into nitrite of ethyl requiring two equivalents of nitrous acid C,EI,N + 2NOs = C4H,N0,+-2HO -j-2N, + + Ethylauiine. Nitrous ether. it appeared that the production of the latter might be greatly facili- tated by the action of the nitrite upon an acid solution of the base. Experiment has borne out this anticipation. In fact it suffices to throw into a solution of hydrochlorate of ethylamine mixed with its own bulk of hydrochloric acid a crystal of nitrite of potzssa when at once together with nitrogen nitrous ether is evolved in consider- able quantity the vapour of' which may be lighted at the mouth of the test-tube.In this manner the conversion can be readily exhi- bited in a lecture-experiment. The yellow aromatic oil which is formed together with the nitrous ether and the production of which I must add is not prevented by the use of an acid solution is obtained in so limited a quantity that f have not yet been able to subject it to a closer examination attractive though the study of a substance produced under so peculiar circumstances must be. I would not have dared toaffirm on the ground of the experiments VOLATILE ORGANIC BASES. detailed the generation of nitrous ether in the above reaction had I not acquired additional support for this position by repeating the same experiment in a less volatile series oxupging a higher position in the system.In their researches on caproic acid Messrs. Brazier and Gossleth bad obtained a considerable quantity of amylamine as a secondary product which these gentlemen kindly placed at my disposal for the experimeiit. Hydrochlorate of amylamine when submitted to the action of a nitrite exhibits exactly the same deportment as ethyla-mine. The experiment is best performed by heating a sclution of nitrite of potassa in a flask connected with a condemer and adding the solution of hydrochlorate of amylamine acidified with hydro-chloric acid in small portions through a funnel-tube the violent effervescence produced upon each addtion being allowed to subside before pouring in a new quantity. By this means an aqueous distillate is obtained with a yellowish oily layer floating upon its surface cxhibitiiig in a remarkable manner the peculiar odour of nitrite of arnyl which for the sake of comparison had been prepared from fusel-oil.The oily substance being separated by means of a pipette the aqueous liquid yielded a little more by saturation with common salt. The whole quantity of oil obtained in this manner amounted to about 4th of an ounce. When dried and sub- jected to distillation the thermometer showed that it was a mixture ebullition commencing at about 90° the thermometer rising slowly to about 1104 and then gradually to 2004 a small quantity of carbon remaining in the retort. During the first part of the distillation a perceptible evolution of red vapours took place evidently arising from the partial decomposition of the nitrite of amyl.A comparative experiment with nitrite of amyl prepared from fusel-oil yielded the same result. The fraction collected between 90° and llO0 when re- distilled exhibited a tendency towards a constant boiling-point a little below looo. The thermometer however rose to nearly 17O0 towards the close of the operation showing that the nitrite of nmyl still con- tained a considerable quantity of other substances. Lest too much should be lost by further rectification the portion collected just below looowas subjected to combustion. 0.3110 of oil gave 0.6125 , carbonic acid and 0.2900 , water. Percentage Carbon . . 53.7; Hydrogen . . . . . 10.36 238 DR.HOFMANN ON THE The formula c,o Hw N 0, requires Carbon . . . . . . 51.21 Hydrogen . . . . 9.41 These numbers showed that the nitrite under examination was still mixed with a quantity of a substance containing more carbon and hydrogen. The boiling-point of pure nitrite of amyl according to Ba1 ar d’s experiment is 96O. Not satisfied with these approximate numbers I endeavoured to obtain additional evidence by the conversion of the nitrite into fusel- oil. After having established by experiment that nitrite of atnyl like its houiologue in the ethyl-series when treated with hydrosul- phate of sulphide of potassium gives rise to the formation of the correlative alcohol with formation of an alkaline polysulphide and ammonia according to the formula C, H, NO + 6NS = C, H, 0 + NH + 2 NO + 6 S.u + Nitrite of amyl. Amyl-alcohol. I subjected the impure nitrite to the same treatment. A violent reaction took place in which the separation of ammonia and sulphur could be traced without difsculty. The resulting fusel-oil at once evident by its nauseous odour was moreover converted into sulphamylic acid by dissolving it in sulphuric acid (when a small quantity of the aromatic oil remained uncombined) and subsequently transformed into a baryta-salt. These experiments leave no doubt respecting the formation of nitrite of amyl by the action of nitrous acid upon arnylamine. In the same reaction however other substances are formed; I say sub- stances because the aromatic oil which boils at the higher tempe- rature when allowed to stand gradually deposits a quantity of shining crystals having a greasy appearance.The same substance which is extremely fusible is usually found to separate on the addition of water to the residue of chloride of potassium in the decomposing flask. I have up to the present moment not the slightest notion respecting the nature of these compounds. Although the difficulty of perfecting these reactions appears at present altogether to preclude the possibility of arriving at the practical formation of propylic and butylic alcohols I was never-theless desirous to see whether propylamine and butylamine would exhibit a similar deportment with nitrites. For this purpose I prepared a quantity of propylamine according VOLATILE ORGANIC BASES.to the directions given by TVertheim by distilling narcotine with an excess of hydrate of potassa.* The aqueous solution of pro-pylamine when supersaturated with hydrochloric acid and treated with nitrate of potassa gave rise to a powerful evolution of nitrogen accompanied by an inflammable gas burning with a green-edged flame. Accordingly propylamine eshibits with nitrous acid a de-portment similar to that of ethylamine; and from analogy we may infer that the burning substance was the nitrous ether of propylic alcohol or nitrite of propyl C H,. N 0,. I am indebted to the kindness of Dr. Anderson of Edinburgh for a small quantity of butylamine prepared by him from Dippel's oil. When dissolved in hydrochloric acid and treated with the nitrite this base likewise evolved a considerable quantity of nitro- gen but no inflammable vapour.The latter circumstance is readily intelligible if we recollect that nitrite of butyl would boil at a rather high temperature at about SO0 a temperature high enough to prevent the compound from evaporating in sufficient quantity in the gas evolved. When the operation was performed in a small retort the evolution of nitrogen was attended with the separation of small oily globules which floated upon the water running down the condenser ; but were dissolved again before reaching the receiver in which an aqueous liquid of a very peculiar odour was collected. Analogy allows us to infer that in this reaction nitrate of butyl C H N 0 the nitrous ether of the butyl-series is formed The regeneration of the alcohols from the nitrites by means of hydrosulphuric acid having been established by experiment it is evident that the deportment of propylamine and butylainine with nitrous acid may one day become the key to the formation of their collateral alcohols as soon as the progress of science shall have taught us simpler and more abundant sources of these bases.In conclusion I wish to draw the attention of the Society to the light which the preceding experiments appear to throw upon some earlier investigations. In 1845 M. Gerhardt observed that the action of nitric acid upon brucine gives rise to the evolution of a gas which burns with a green flame and exhibits some of the properties of nitrous ether.The formation of this ether in the process alluded to was subsequently * By the distillation of narcotine with potassa in addition to an aqueous solution of propylamine an oily base boiling apparently at a very high temperature was formed which deserves to be examined. The odour of propylamine remarkably resembles that of lobster in an early stage of putrefaction. 240 AI. CA'LHOUItS ON doubted by Liebig who on repeating the experiment obtained a liquid boiling at a temperature (from 70° to 7P),much higher than the boi1ing:point of nitrous ether (16O.5). It is evident that the action of nitric acid upon brucine induces the formation of various substances. The existence among the natural alkaloids of ettiylated bases which I suggested on a former occasion and which appears to be borne out by new facts such as the formation of methylinline from caffeine or of propylamine from narcotine renders it probable that part of the metamorphosis caused by nitric acid is due to the formation of nitrous acid which subsequently acts as in the foregoing experiments I have distilled an acid solution of hydrochlorate of brucine with nitrite of potassa and find that this reaction gives rise to the evolution of a considerable quantity of the inflammable gas burning with a green-edged flame which is obtained by directly dissolviiig bruciiie in nitric acid.