BENZYL PHOSPHINES AND THEIR DERIVATIVES. 593 



eight hours, a complete reaction occurred, the tubes when cold containing a crystalline mass 

 consisting exclusively of the hydriodates of the primary and secondary bases, the former 

 being the chief product, while the latter was only formed in small quantities. The 

 separation of the two was accomplished in the simplest manner possible, the addition of 

 water to the product of reaction liberating the primary phosphine alone, which was dis- 

 tilled off in a hydrogen atmosphere, while the secondary phosphine was subsequently set 

 at liberty by the action of an alkali. 



Thus Hofmann discovered for the first time a general method for preparing primary 

 and secondary phosphines, the reaction being exactly complementary to that by which 

 he had obtained the tertiary and quaternary compounds ; like it the method was 

 distinguished by its simplicity and the readiness with which it may be carried out. 



By its means he prepared methyl,* ethy],t propyl,^ butyl, § amyl,|| and benzyl 1 

 phosphines. 



(5) Michaelis' Methods. — Hofmann's methods, although of excellent service for 

 obtaining the phosphines of those radicals which form alcohols, could not be employed 

 in the preparation of phosphines containing purely aromatic radicals. He in vain 

 endeavoured to obtain phenyl phosphines, ## but neither by the action of chlorobenzol 

 on phosphonium iodide, nor by heating a mixture of phenol and phosphonium iodide, 

 was a trace of those substances produced, and he was equally unsuccessful in his 

 attempts to prepare tolyl phosphines. 



Michaelis, on the other hand, by approaching the question from an entirely different 

 direction, not only succeeded in obtaining all the phenyl phosphines, but also in discover- 

 ing a fairly general method for the production of primary phosphines. The substance 

 forming the starting-point for the preparation of phosphines by these methods is trichloride 

 of phosphorus. One atom of chlorine is first replaced in that body by one or other of 

 the following processes :- — 



(1) The mixed vapours of a hydrocarbon and the trichloride are repeatedly passed 



through a red hot tube. Thus, when benzol is employed, ''phosphenyl" chloride is 



obtained — 



PC1 3 +C 6 H 6 = (C 6 H 5 )PC1 2 +HCL 



(2) A mercury ether is heated with the trichloride under pressure. Thus, when 

 mercury ethyl is employed, ethyl-phosphorus chloride is obtained together with ethyl 



chloride of mercury — 



PCl 3 -l-(C 2 H 5 ) 2 Hg = (C 2 H 5 )I > Cl 2 +Hg(C 2 H 5 )Cl. 



(3) By digesting a hydrocarbon with the trichloride and aluminum chloride, the 

 reaction being the same as 1. Other substances besides hydrocarbons yield substituted 

 phosphorus chlorides when submitted to this reaction. Thus a mixture of acetone, 



* Hofmann, Berichte, iv. (1871) p. 430. t Hofmann, Ibid., iv. (1871) p. 605. 



X Ibid., vi. (1873). p. 292. § Ibid., vi. (1873) p. 296. 



|| Ibid., vi. (1873) p. 297. II Ibid., v. (1872) p. 100. 

 ** Ibid., Berichte, v. (1872) p. 100. 



