BENZYL PHOSPHINES AND THEIR DERIVATIVES. 623 



Action of Heat on Dibenzyl Phosphinic Acid. — Preliminary experiments with the 

 pure acid in a test-tube seemed to show that it distilled unchanged. A quantity was 

 heated in a distilling flask. It boiled above the boiling point of mercury, and the 

 distillate on cooling formed a semi-solid crystalline mass, smelling very slightly of the 

 primary phosphine. As the distillation proceeded, the residue in the flask darkened. 

 The whole of the distillate was warmed with caustic potash, in which most of it seemed 

 to dissolve, but a crystalline residue remained saturated with some oily matter. The 

 solution was filtered from this residue, precipitated with excess of hydrochloric acid, and 

 the washed precipitate recrystallised from alcohol. It separated in characteristic thin 

 plates of dibenzyl phosphinic acid, and was identified by its melting point and other 

 properties as that body. The crystalline matter insoluble in potash was well washed 

 with water and then crystallised from hot alcohol, when it separated in needles, having 

 the melting point of tribenzyl phosphine oxide, and it was further identified as that body 

 by the production of the characteristic bromine compound. 



The residue in the distilling flask was black and tarry, and was dissolved when boiled 

 with caustic soda. The solution thus obtained, when acidulated with hydrochloric acid, 

 gave a crystalline precipitate (probably crude dibenzyl phosphinic acid), and when filtered 

 from this, was found to contain abundance of phosphoric acid. 



We may conclude from the above results that when dibenzyl phosphinic acid is heated 

 it volatilises in a great measure unchanged, but that a portion decomposes, giving 

 phosphoric acid, tribenzyl phosphine oxide, and toluol — 



2(C 7 H 7 ) 2 HP0 2 = (C 7 H 7 ) 3 PO + HP0 3 + C 7 H 8 . 



Action of Pentachloride of Phosphorus on Dibenzyl Phosphinic Acid. — 10 grms. of 

 the acid and 10 grms. of pentachloride of phosphorus* were placed in a distilling flask, and 

 the latter gradually treated in a paraffin-bath. A reaction soon occurred, and torrents of 

 hydrochloric acid gas came off. As soon as the action had moderated the product was 

 distilled. 7 grms. of liquid came off before 110° C, then the thermometer rose slowly to 

 300° C, without remaining constant at any temperature, during which about 7 grms. of 

 an oily liquid came off. By this time the residue in the distilling flask was very syrupy 

 and of a brown colour, and on admitting air it smoked, and seemed to be giving off free 

 phosphorus. 



The two distillates, when redistilled, passed over in a great measure below 110° C. 

 They were shaken with water, and after decomposition an oily liquid floated on the surface 

 (in all about 2 grms.), which was unmistakably benzyl chloride. We could not isolate 

 any acid chloride, (C 7 H 7 ) 2 P0C1, and a profound decomposition seems to occur, possibly 

 according to the equation — 



(C 7 H 7 ) 2 HP0 2 + 3PC1 5 = 2PCLO + HC1 + 2PC1 3 + 2C 7 H 7 C1 . 



* The quantities required for the equation (C 7 H 7 ) 2 HP0 2 +PCl 5 = (C 7 H 7 ) 2 POCl + HCl+POCl 3 are 10 grms. of the 

 acid and 8'5 grms. of pentachloride of phosphorus. 



VOL. XXXV. PAST II, (NO. 15). 5 G 



