yield compounds of the type C6H5SO2NR2, insoluble in alkalies (O. Hinsberg, Ber., 1890, 23, p. 2963). Primary amines heated with carbon bisulphide in alcoholic solution are converted into mustard oils, when the dithiocarbamate first produced is heated with a solution of mercuric chloride.
Methylamine, CH3NH2, occurs in Mercurialis perennis, in bone-oil, and herring brine. It is also a decomposition product of many alkaloids. At ordinary temperatures it is a gas, but may be condensed to a liquid which boils at −6° C. It has a strong ammoniacal smell, burns readily and is exceedingly soluble in water. Its critical temperature is 155° C. and critical pressure 72 atmos. (C. Vincent, J. Chappuis; Jahresb., 1886, p. 202). Dimethylamine, (CH3)2NH, is found in Peruvian guano. It is a heavy vapour which condenses at 7° C. to a liquid, having a pronounced fish-like smell. Trimethylamine, (CH3)3N, is very similar to dimethylamine, and condenses to a liquid which boils at 3·2–3·8° C. It is usually obtained from “vinasses,” the residue obtained from the distillation of beet sugar alcohol, and is used in the manufacture of potassium bicarbonate by the Solvay process, since its hydrochloride is much more soluble than potassium carbonate. Tetramethylammonium iodide, N(CH3)4I, is the chief product obtained by the action of methyl iodide on ammonia (Hofmann). It crystallizes in quadratic prisms and has a bitter taste. By warming its aqueous solution with an excess of silver oxide it is converted into tetramethylammonium hydroxide, N(CH3)4OH, which crystallizes in hygroscopic needles, and has a very alkaline reaction. It forms many crystalline salts and absorbs carbon dioxide. It precipitates many metallic hydroxides. On dry distillation it is resolved into trimethylamine and methyl alcohol. If the nitrogen atom in the quaternary ammonium salts be in combination with four different groups, then the molecule is asymmetrical, and the salt can be resolved into optically active enantiamorphous isomerides. W. J. Pope (Jour. Chem. Soc., 1901, 79, p. 828) has resolved benzyl-allyl-phenyl-methylamine iodide by boiling with silver d-camphorsulphonate in a nearly anhydrous mixture of acetone and ethyl acetate. The silver iodide is separated and the solvent distilled off. The residue crystallizes slowly, and the crystalline product is almost wholly d-benzyl-allyl-phenyl-ammonium-d-sulphonate, the corresponding l-compound remaining as a syrupy residue. The corresponding iodides are obtained by the addition of potassium iodide to solutions of the sulphonates, and are optically active antipodes.
Diamimes.—The diamines contain two amino groups and bear the same relation to the glycols that the primary monamines bear to the primary alcohols. They are of importance, since the higher homologues are identical in many cases with the ptomaines produced by the putrefactive action of some bacteria on albumen and other related substances. Ethylene diamine, C2H4(NH2)2, may be prepared by heating ethylene dibromide with alcoholic ammonia to 100° C. (F. S. Cloez, Jahresb., 1853, p. 468); or by the action of tin and hydrochloric acid on cyanogen (T. Fairley, Ann. Suppl., 3, 1864, p. 372). It is an alkaline liquid, which, when anhydrous boils at 116·5° C. Nitrous acid converts it into ethylene oxide. It combines directly with many metallic salts. (See S. F. Jörgensen, Jour. pr. Chem., 1889 (2), 39, p. 8.) Trimethylene diamine, NH2·(CH2)3·NH2, is prepared by the action of ammonia on trimethylene bromide (E. Fischer, Ber., 1884, 17, p. 1799). It is a liquid which boils at 135–136° C., and is readily soluble in alcohol, ether, chloroform and benzene. Tetramethylene diamine (putrescine), NH2·(CH2)4·NH2, is prepared by reducing ethylene dicyanide (succinonitrile) with sodium in absolute alcoholic solution (A. Ladenburg, Ber., 1886, 19, p. 780). It melts at 27° C., and is easily soluble in water. Pentamethylene diamine (cadaverine), NH2·(CH2)5·NH2, is prepared by reducing trimethylene cyanide in ether solution by zinc and hydrochloric acid (A. Ladenburg, Ber., 1883, 16, p. 1151). J. v. Braun (Ber., 1904, 37, p. 3583) has prepared pentamethylene derivatives from piperidine by the action of phosphorus pentachloride. On heating piperidine with phosphorus pentachloride to 200° C. in a sealed tube pentamethylene dichloride is obtained, and this on treatment with potassium phthalimide gives a condensation product of composition, C6H4[CO]2N(CH2)5N[CO]2C5H4, which is finally hydrolysed by hydrochloric acid. Cadaverine is a syrup at ordinary temperatures, and boils at 178–179° C. It is readily soluble in water and alcohol, but only slightly soluble in ether.
Aromatic Amines.—The aromatic amines in some respects resemble the aliphatic amines, since they form salts with acids, and double salts with platinum chloride, and they also distil without decomposition. On the other hand, they are much weaker bases than the aliphatic amines, their salts undergoing hydrolytic dissociation in aqueous solution. The primary aromatic amines may be prepared by the reduction of the nitro-hydrocarbons, the reducing agents used being either alcoholic-ammonium sulphide (N. Zinin), zinc and hydrochloric acid (A. W. Hofmann), an alcoholic solution of stannous chloride (containing hydrochloric acid) (R. Anschutz, Ber., 1886, 19, p. 2161), tin and hydrochloric acid, or, on the manufacturing scale, iron and hydrochloric acid. They may also be obtained by the reduction of nitroso compounds and of hydrazo compounds and of hydrazones (J. Tafel, Ber., 1886, 19, p. 1924), by distilling the amido-acids with lime, by heating phenols with zinc chloride ammonia (V. Merz, Ber., 1880, 13, p. 1298), and by heating the secondary and tertiary bases with concentrated hydrochloric acid to about 180° C.
At a temperature of about 300–400° C. the alkyl chloride formed in this reaction attacks the benzene nucleus and replaces hydrogen by an alkyl group or groups, forming primary amines homologous with the original amine; thus methylaniline hydrochloride is converted into para- and ortho-toluidine hydrochloride, and trimethyl phenyl ammonium iodide is converted into mesidine hydriodide. It is to be noted that only traces of the aromatic amines are produced by heating the halogen substituted benzenes with ammonia, unless the amino group be situated in the side chain, as in the case of benzylamine.
The primary amines are colourless liquids or crystalline solids, which are insoluble in water, but readily soluble in the common organic solvents. When heated with alkyl or aryl iodides, they are converted into secondary and tertiary amines. Concentrated nitric acid attacks them violently, producing various oxidation products, but if the amino group be “protected” by being previously acetylated, then nitro derivatives are obtained. When heated with concentrated sulphuric acid for some time, they are sulphonated. They form condensation products with aldehydes, benzaldehyde and aniline forming benzylidene aniline, C6H5N: CHC6H5, and when heated with acids they form anilides. They give the isonitrile reaction (see above) when warmed with chloroform and a caustic alkali, and form alkyl thioureas when heated with an alcoholic solution of carbon bisulphide. When warmed with a solution of nitrous acid, they are converted into phenols; if, however, nitrous acid be added to an ice-cold solution of a primary amine in excess of mineral acid, a diazonium salt is formed (see Azo Compounds and Diazo Compounds), or in absence of excess of acid, a diazoamine is produced.
The secondary amines may be of two types—namely, the purely aromatic amines, and the mixed secondary amines, which contain an aromatic residue and an alkyl group. The purely aromatic amines result upon heating the primary amines with their hydrochlorides, and, in some cases, by heating a phenol with a primary amine and anhydrous zinc chloride. The mixed secondary amines are prepared by the action of alkyl iodides on the primary amines, or by heating salts of the primary amine with alcohols under pressure. The mixed secondary amines have basic properties, but the purely aromatic secondary amines are only very feeble bases. Both classes readily exchange the imide hydrogen for acid radicals, and give nitrosamines with nitrous acid. The secondary amines do not give the isonitrile reaction.
The tertiary amines may also be of two types, the purely aromatic and the mixed type. The mixed tertiary amines are produced by the action of alkyl halides on the primary amines. The simplest aromatic tertiary amine, triphenylamine, is prepared by the action of brombenzene on sodium diphenylamine (C. Heydrich, Ber., 1885, 18, p. 2156). The simplest aromatic monamine is aniline (q. v.), and the simplest mixed amines are
