Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/587

AMINES.] CHEMISTRY 575 Like ammonium salts, these amines form yellow crystal line double salts when their hydrochlorides are mixed with a solution of platinic chloride. The general formula of these salts (A representing amine) is 2AHC1, PtCl 4 . Tertiary amines unite directly with iodides of C n H 2n+1 radicles, forming compounds of the type of haloid ammo nium salts : N(C 2 H 5 ) 3 + CjH 5 I = N(C,H 5 ) 4 I Triethvlamine. Ethyl iodide. Tetrethylammo- nium iodide. These compounds do not again furnish the tertiary amine on treatment with KHO, but on heating with Ag 2 O and water bodies such as tetrethylammonium hydroxide, N(C 2 H 3 ) 4 HO, are produced. These bodies are highly caustic bases analogous to ammonium hydroxide, but more like the fixed alkalies in their general behaviour. The amines of the present group are susceptible of metamerism and isomerism. For example : Metamedc...N(C 3 H 7 )H 2 , N(CH 3 )(C 2 H 5 )H , N(CH 3 ) 3 . Propylamine. Methyl-ethylamine. Trimethylamine. Ismeric...N(C 3 H 7 )H 2 , N[CH(CH 3 ) 2 ]H 2 . Propylamine. Pseudopropylamine. By the action of nitrous acid primary amines are con verted into nitrites, which are decomposed on heating, with the formation of the corresponding alcohol : N(C n H 2n+1 )H,.HX0 2 = C n H 2n+1 .HO + OH 2 + N 2 . The alcohols produced by this reaction are isomeric and not identical with those of the radicle from which the amine is derived in cases where such isomerism is possible. The action of nascent hydrogen on the nitriles gives rise to the formation of amines : C ;i H, n+1 .CX + 2H 2 = X(CH 2 C n Ho n+1 )H 2 . The nitriles can be obtained from the alcohols by com bining the latter with sulphuric acid, converting the sulpho-acid thus produced into a potassium, salt, and dis tilling this with potassium cyanide (p. 566). By combining all these reactions the homologous series of alcohols can be ascended. To give an illustration : Methyl alcohol is combined with sulphuric acid, and the resulting sulpho- acid converted into potassium methylsulphate. This latter salt is mixed with potassium cyanide and submitted to dry distillation, when methyl cyanide (acetonitrile) is produced ; this when acted on by nascent hydrogen is converted into ethylamine, which by the action of nitrous acid is trans formed into ethyl alcohol. By a similar series of reactions ethyl alcohol can be converted into propylamine, which by the action of HXO 2 is converted into pseudopropyl alcohol. Isocyanides or C arbammes. These compounds, meta- meric with the cyanides of hydrocarbon radicles (p. 555), may be regarded as formed on the type of ammonium salts ; thus (X representing the acid radicle) X T H 4 X N T C IV R Ammonium salts. Carbamine. Most of the reactions made use of in preparing the cyanides give rise to the simultaneous formation of iso cyanides (see p. 555) ; the latter bodies are in excess when the iodides of the radicles are made to act upon silver cyanide. Isocyanides are also obtained by beating primary amines with chloroform and caustic potash : XR H 2 + CHC1 3 + 3KHO = N C : This reaction affords a ready means of distinguishing primary amines, as the isocyanides are at once detected, even in the smallest traces, by their powerful and nauseous odours. The carbamines reduce many metallic oxides (such as HgO , Ag 2 O , &c.) with the formation of cyanates of the contained hydrocarbon radicles. They possess pro perties decidedly more basic than their metamerides, com- billing energetically with acids to form salts. When heated in sealed tubes the isocyanides are partially trans formed into the corresponding nitriles. Monamines containing C n H 2rt _ 1 radicles are represented by allylamine, N(C 3 H 5 )H, . Monamines containing C s H 0n _ 7 radicles. These bases belong to two isomeric series corresponding to the alcohols of the benzyl series and to the phenols. This relationship is exemplified by the following formulae : C 6 H 4 (NH 2 ).CH 3 C 6 H 5 .CH 2 (NH 2 ) Toluidine. isomeric with Benzylamine CTT /VTJ //""TT O "CT f^TT f"*14 TTT 6 tL 3 (JNhL 2 ).(bhL 3 ) 2 L, 6 il 4 .L<.tl 3 .^il 2 ^>.ti 2 ; Xylidine isomeric with Xylyiamine. The following are the more important amines of the present group : Primary. Phenylamine (aniline) C 6 H 5 (XH 2 ) Benzylamine C 7 H 7 (NH 2 ) Xylyiamine C 8 H 9 ( XH 2 ) Cymylamine C IO H I3 (NH 2 ) Toluidine C 6 H 4 (NH 2 ).CH 3 Xylidine C 6 H 3 (NH 2 ).(CH 3 ), Cumidine C 6 H 2 (NH 2 ).(CH 2 ) 3 Cymidine C 6 H(XH 2 ).(CH 3 ) 4 Secondary. Dibenzylamine (C 7 H 7 ). 2 (XH) Dixylylamine (C 8 H 9 ) 2 (NH) Dicymylamine (C 10 Hi 3 ).,(NH) Diphenylamine (C 6 H 5 ). 2 (NH) Ethyl-phenylamiue (C C H 5 )(C 2 H S )(XH) Methyl-phenylamine (C 6 H 5 )(CH 3 )(NH) Tertiary. Tribenzylamine (C 7 H 7 ) 3 N Trixylylamine (C 8 H 9 ) 3 X Tricymylamine (C 10 H i 3 )sN Triphenylamine (C 6 H 5 ) 3 N Dimethyl-phenylamine (C 6 H 5 )(C H 3 ),N Dimethyltoluidine (C B H 4 . CH 3 )("CIT 3 ) 2 y Dimethylxylidine {C 6 H 3 (CH 3 ). 2 ](CH 3 ). 2 N Dimethylcumidine [C 6 H. 2 (CH 3 ) 3 ](CH 3 ) 2 N Dimethylcymidine [C 6 H (CH 3 ) 4 ](CH 3 ) 2 N The amines of the benzyl series are obtained by the action of the chlorides of the corresponding radicles on ammonia. Toluidine and its homologues are prepared by reducing the nitro-derivatives of the corresponding hydro carbons by means of acetic acid and iron (ferrous acetate), ammonium sulphide, &c. : C H 5 (N0 2 ) + 3SH 2 = C 6 H 5 (NH 2 ) + 2OH 2 + 3S. Nitrobenzene. Amidobenzene (aniline). These latter amines, which may be regarded as amido- benzene, in which 1, 2, 3, &c., H atoms are replaced by R , R 2 , R 3 , &c., are susceptible of the isomeric modifica tion dependent on the relative positions of the replaced H atoms. Thus we have C 6 (NH )(CH 3 )HHHH 1 2 3456 C 6 (NH 2 )H(CH 3 )HHH Orthotoluidine. Metatoluidine. C 6 (NH 2 )HH(CH 3 )HH 1 23 4 56 Paratoluidine. All these amines are basic colourless liquids, more or less oily, and possessing highly characteristic odours. They combine with acids forming crystalline salts, which are decomposed by caustic alkalies with the liberation of the amine. Phenylamine or aniline, the first member of the present series of primary amines, may be regarded as the first homologue of both the above isomeric series. It derives its name from the indigo-plant (Indigofera Anil}, as it was first obtained by distilling indigo with caustic potash. Aniline is found in small quantities in coal-tar oils, but is manufactured on the large scale by reducing nitrobenzene

with iron and acetic acid. Aniline is, when pure, a colour-