BENZYL PHOSPHINES AND THEIR DERIVATIVES. 573 



These results show that the product of the reaction yielded nearly 40 per cent, of 

 its weight of tribenzyl phosphine oxide, and contained some benzyl phosphinous acid. # 



Experiment 2. — This experiment was made chiefly with the view to ascertaining 

 whether the reaction gives rise to a phosphonium salt in addition to the tertiary phosphine. 

 2 grms. of the phosphine and 2 grms. of chloride of benzyl were heated to 160° C. for five 

 or six hours. The tube then contained a syrupy liquid and some amorphous phosphorus. 

 On opening it there was very decided pressure from phosphuretted hydrogen (proved 

 by its action on nitrate of silver). The viscous liquid fumed powerfully from escape of 

 hydrochloric acid, and on adding water all the phenomena described in Experiment 1 

 were reproduced. After thorough oxidation the solid mass was boiled with water, and 

 the solution on cooling gave the characteristic long needles of chloride of tetrabenzyl 

 phosphonium. These, after repeated recrystallisation from water, had a melting point 

 of 228° "5 C. — exactly that of the pure chloride — and we estimated that over 1 grm. had 

 been formed. 



The residue insoluble in water was extracted with potash, the solution filtered, and 

 treated with hydrochloric acid, when no trace of dibenzyl phosphinic acid was precipitated. 

 But on boiling the insoluble residue with alcohol plenty of tribenzyl phosphine oxide was 

 obtained. 



The above experiments fully confirm the results of those which we made with benzyl 

 iodide. They show that the action of the haloid derivatives of benzyl on the primary 

 phosphine varies not only with the particular halogen present, but also with the conditions 

 under which the action occurs. Thus, when benzyl iodide is employed at ordinary 

 temperatures, the secondary phosphine is the chief product, while a considerable quantity 

 of the tertiary phosphine is also formed, and only a small quantity of the phosphonium 

 salt, but we suspect that at higher temperatures the proportions of these three products 

 would not be the same. 



With benzyl chloride no action occurs at ordinary temperatures, but under the 

 influence of heat a reaction takes place, the tertiary phosphine and the phosphonium 

 chloride being formed, while if the temperature is high the phosphonium salt is the chief 

 product, and no secondary phosphine is produced at all. 



Properties of Dibenzyl and Tribenzyl Phosphine. — Although we have not isolated 

 the first of these in the pure state, and have only obtained the second in small quantities, 

 we have so often examined a mixture of the two that we are enabled to state with 

 probable correctness what their chief properties are. 



Dibenzyl Phosphine. — A liquid which cannot be distilled even in vacuo without 



considerable decomposition. This decomposition gives rise to the primary and tertiary 



bases, 



2(C 7 H 7 ) 2 HP^(C 7 H 7 )PH 2 + (C 7 H 7 ) 3 P . 



Dibenzyl phosphine combines with hydriodic acid, and probably with other hydracids, 



* The rest of the product was evaporated down with aqueous potash, and also yielded oxide of tribenzyl phosphine 

 in abundance, some benzyl phosphinous acid, but scarcely a trace of dibenzyl phosphinic acid. 



