BENZYL PHOSPHINES AND THEIR DERIVATIVES. 



531 



General Properties of the Secondary Phosphines. 

 The following secondary phosphines have been obtained : — 



Name. 



Condition. 



Boiling Point. 



Dimethyl 

 Di-ethyl 



Di-isopropyl 



Di-isobutyl 



Di-isoamyl 



Di-phenyl 



Methyl-isopropyl 



Iso-propyl, isobutyl 



phosphine ( x ), 



„ o, 



„ ( 3 ), 



„ <\) 



( 5 )> 



( e ), 



CO. 



( 8 ), 



Liquid. 



25 



85 



118 



153 



210-215 



280 (about) 



78-80 



139-140 



( x ) Hofmann, Berichte, iv. (1871) p. 610. ( 2 ) Hofmann, Berichte, iv. (1871) p. 433. , 



( 3 ) Ibid. Ibid. vi. (1873) p. 294. ( 4 ) Ibid. Ibid. vi. (1873) p. 296. 



( 5 ) Ibid. Ibid. vi. „ p. 298. ( 6 ) Michaelis, Ibid. xv. (1882) p. 80lA. 



C) Ibid. Ibid. vi. „ p. 295. ( 8 ) Hofmann, Ibid. vi. (1873) p. 300. 



* Dibenzyl phosphine is not mentioned, for reasons which will become apparent in the body of the paper. 



All the secondary phosphines obtained as yet are liquids, having a powerful odour. 

 They are insoluble in water, but soluble in ether, &c. 



They have as a rule a strong attraction for oxygen, fuming and growing hot on 

 exposure to the air, and often inflaming spontaneously. In some cases they appear to 

 have even a greater affinity for oxygen than the primary bases. This is so according to 

 Hofmann with all the secondary phosphines of the fatty series which he obtained. But 

 apparently it is not the case with diphenyl phosphine. The products of this spontaneous 

 oxidation do not appear to have been examined. But the products of their oxidation by 

 nitric acid have been investigated, chiefly by Hofmann.* They are in all cases phosphinic 

 acids, R 2 PH0 2 , which are monobasic, and no doubt have the constitution, 



R 





HO 



These acids are probably also produced when the chlorides E 2 PC1 are oxidised by 

 nitric acid. Such is at least the case with (C G H 5 ) 2 PC1. Some of them can be distilled 

 unchanged, e.g., dimethyl phosphinic acid; others, e.g., diphenyl phosphinic acid, lose 

 water, and give pyro acids. 



Secondary phosphines combine with acids, the resulting salts being far more stable 

 than those of the primary bases. Thus in most cases they are not decomposed by 

 water, though some are (e.g., salts of diphenyl phosphine). Comparatively little is 

 known regarding secondary phosphines, and very few of their compounds have been 

 investigated. 



Both sulphur and bisulphide of carbon act upon them, but the products have not 



* Hofmann, Berichte, v. (1872) p. 104, and vi. (1873) p. 303. 



