Fischer (Berichte, 1897, 30, p. 2238) by heating 2.6.8-trichlorpurin with 10 times its weight of ammonia for six hours at 100° C.; by this means 6-amino-2.8-dichlorpurin is obtained, which on reduction by means of hydriodic acid and phosphonium iodide is converted into adenine.
Phosphonium Salts.-The chloride, PH 4 C1, was obtained as a crystalline solid by Ogier (Comptes rendus, 1879, 89, p. 705) by combining phosphine and hydrochloric acid gas under a pressure of from 14-20 atmospheres; it can also be obtained at -30° to -35° C. under ordinary atmospheric pressure.
Just as the amines are derived from ammonia, so from phosphine are derived the primary, secondary and tertiary organic phosphines by the exchange of hydrogen for alkyl groups, and corresponding to the phosphonium salts there exists a series of organic phosphonium bases.
The quaternary phosphonium salts resemble the corresponding nitrogen compounds.
They are stable towards aqueous alkalis, but on digestion with moist silver oxide yield the phosphonium hydroxides, which are stronger bases than the caustic alkalis.
The oxide P 2 0 was obtained by Besson (Comptes rendus, 1897, 124, p. 763; 1901, pp. 132, 1556) by heating a mixture of phosphonium bromide and phosphorus oxychoride in sealed tubes to 50°.