[662] Brieger has also given to the pure base a boiling-point of 175°.
When cadaverine is treated with methyl iodide, two atoms of hydrogen may be replaced with methyl, forming the base C5H12(CH3)2N2; the platinochloride of this last base crystallises in long red needles.
Cadaverine forms well-defined crystalline salts as well as compounds with metals.
Cadaverine hydrochloride, C5H14N22HCl, crystallises in needles which are deliquescent, or it may be obtained from an alcoholic solution in plates. The crystals are insoluble in absolute alcohol, but readily soluble in 96 per cent. alcohol. Putrescine hydrochloride, on the other hand, is with difficulty soluble in alcohol of that strength; hence the two hydrochlorides can be separated by taking advantage of their difference in solubility in 96 per cent. alcohol; but the better method for separation is the benzoyl-chloride process ([p. 487]). On dry distillation, cadaverine hydrochloride decomposes into NH3,HCl and piperidine C5H11N. The compound with mercury chloride—C5H14N22HCl,4HgCl2 (Hg = 63·54 per cent.); melting-point, 214°-216°—is insoluble in alcohol and in cold water; this property is also useful to separate it from putrescine, the mercury compound of which is soluble in cold water. The platinochloride, C5H14N22HCl,PtCl4 (Pt = 38·08 per cent.), crystallises in dirty red needles; but, by repeated crystallisation, it may be obtained in clear chrome yellow, short, octahedral prisms; it is soluble with difficulty in hot water, insoluble in cold water. The salt decomposes at 235°-236°.
The aurochloride—C5H14N22HCl2AuCl (Au = 50·41 per cent.), melting-point 188°—crystallises partly in cubes and partly in needles, and is easily soluble in water.
Other salts are the picrate, C5H14N22C6H2(NO2)3OH, melting-point 221° with decomposition; with difficulty soluble in cold, but dissolving in hot water, and insoluble in absolute alcohol. There are also a neutral oxalate, C5H14N2,H2C2O4 + 2H2O, melting-point 160°; and an acid oxalate, C5H14N22H2C2O4 + H2O, melting-point 143° with decomposition; both these oxalates are insoluble in absolute alcohol.
Cadaverine dibenzoyl—C5H10(NHCOC6H5)2, melting-point 129°-130°—crystallises in needles and plates, soluble in alcohol and slightly soluble in ether, insoluble in water.
It is not acted on by hot dilute acids or alkalis, and when dissolved in concentrated hydrochloric acid and alcohol it is, only after prolonged boiling, decomposed into benzoic acid and the free base. The benzoic acid after getting rid of the alcohol by evaporation, can be removed by shaking up with ether; then the hydrochloride can be decomposed by an alkali and the free base obtained, or the platinum salt of cadaverine may be formed by precipitation with platinum chloride. Should cadaverine and putrescine be in the same liquid, the dibenzoyl compounds may be separated as follows:—the crystalline precipitate is collected on a filter, washed with water until the filtrate runs clear, and then dissolved in warm alcohol; this solution is poured into twenty times its volume of ether and allowed to stand; after a short time crystals form of the putrescine compound, which are far less soluble in alcohol than those of cadaverine dibenzoyl; these crystals are filtered off and repeatedly crystallised from alcohol until the melting-point is about 175°-176°. The filtrate contains the cadaverine compound; this latter is recovered by evaporating off the ether-alcohol.
§ 665. Putrescine—Tetramethylenediamine, C4H12N2=NH2CH2CH2CH2CH2NH2.