1872.] Dr. A. W. Hofmann on the Phosphorus Bases. 



237 



chloride and phosphonium iodide to meet under appropriate circumstances, 

 an aromatic phosphorus base would be obtained. 



Benzyl 'phosphine. 



c, H,| 



C. H„ P = H IP. 



H J 



For the preparation of this body it is not necessary to employ the 

 benzyl chloride in its pure state. It suffices to operate with toluol chlo- 

 rinated whilst hot, which boils between 150° and 180°. The substances 

 acting on one another are employed in the same proportions which, in the 

 methyl and ethyl series, are known toyield satisfactory results, namely 2 mol. 

 of benzyl chloride, 2 mol. of phosphonium iodide, and 1 mol. of zinc oxide. 

 A digestion of six hours' duration at 160° is sufficient for the formation of 

 benzylphosphine. When the reaction is finished the digestion-tubes con- 

 tain a white mass of crystals, which is generally forced out by the phos- 

 phoretted hydrogen escaping when the tubes are opened. When the 

 product of the reaction was distilled with the vapour of water, an oily 

 liquid, heavier than water, possessing an extremely characteristic persis- 

 tent odour, passed over. This was separated from the water by means of 

 a separating funnel, dried by allowing it to stand on caustic potass, and 

 submitted to fractional distillation in a current of hydrogen. It com- 

 menced boiling a few degrees above 100°; the mercury then rose rapidly 

 to 180°, at which temperature a large quantity of a colourless, powerfully 

 refractive liquid distilled. That passing between 180° and 190° was col- 

 lected apart from the earlier distillate, consisting chiefly of toluol (which 

 is regenerated from the benzyl chloride by the phosphonium iodide). The 

 liquid boiling at 180° is benzylphosphine ; the residue in the retort con- 

 tains dibenzylphosphine and other products. 



Purified by a second distillation in a current of hydrogen, benzylphosphine 

 is found to have the constant boiling-point 180°. In contact with the 

 air the aromatic phosphorus base attracts oxygen with such avidity 

 that the thermometer rises to 100° and more, and thick white clouds are 

 formed. Benzylphosphine is insoluble in water, but easily so in alcohol 

 and ether. The aromatic phosphorus base shares the characteristic property 

 of the other primary phosphines, viz. that of forming a crystallizable iod- 

 hydrate. This is obtained by mixing the phosphine with fuming iodhv- 

 dric acid, when it falls as a white and, apparently, amorphous mass. The 

 insolubility of the iodine compound presents an easy method of recovering 

 any benzylphosphine that may have passed over in the first distillate 

 containing toluol. The white precipitate of benzylphosphine iodhydrate 

 dissolves on warming in iodhydric acid, and forms, as the solution cools, 

 white needles, often more than a centimetre long, which, in contact with 

 water, are decomposed into the acid and base. By washing with dry 

 ether and drying in a stream of hydrogen at 100°, the iodhydrate may 



