The monamines are similar to ammonia in their reactions; some of them are stronger bases; for instance, ethylamine expels ammonia from its salts. The first members of the series are combustible gases of pungent odour, and easily soluble in water; the higher homologues are fluids; and the still higher members solids.
The hydrochlorides are soluble in absolute alcohol, while chloride of ammonium is insoluble; this property is taken advantage of for separating amines from ammonia. The amines form double salts with platinic chloride; this is also utilised for recognition, for the purpose of separation, and for purification; for instance, ammonium-platinum-chloride on ignition yields 43·99 per cent. of platinum, and methylamine-platinum-chloride yields 47·4 of platinum. It is comparatively easy to ascertain whether an amine is primary, secondary, or tertiary.
The primary and secondary amines react with nitrous acid, but not the tertiary; the primary amines, for instance, are converted into alcohols, and there is an evolution of nitrogen gas; thus methylamine is decomposed into methyl alcohol, nitrogen, and water.
CH3NH2 + (OH)NO = CH3(OH) + N2 + H2O.
The secondary amines, treated in the same way, evolve no nitrogen, but are converted into nitrosamines; thus dimethylamine, when treated with nitrous acid, yields nitrosodimethylamine,
(CH3)2NH + (OH)NO = (CH3)2(NO)N + H2O;
and the nitrosamines respond to the test known as Lieberman’s nitroso-reaction, which is thus performed:—The substance is dissolved in phenol and a few drops of concentrated sulphuric acid added. The yellow colour at first produced changes into blue by adding to the acid liquid a solution of potash.
The primary amines, and the primary amines alone, treated with chloroform and alcoholic potash, yield the peculiarly offensive smelling carbylamine or isonitrile (Hofmann’s test),
| V | |
| NH2(CH3) + CHCl3 + 3KOH = C≣N | -CH3 + 3KCl + 3H2O. |
Again the primary bases, when treated with corrosive sublimate and carbon disulphide, evolve sulphuretted hydrogen, and mustard oil is produced, e.g.,