536 PROF. LETTS AND MR R. F. BLAKE ON 



The action of heat upon the salts of the phosphoniums has been investigated in a 

 number of cases, partly by one of us * and N. Collie, and partly by the latter chemist 

 alone. 



As regards the haloid salts, the chlorides decompose almost quantitatively into a 

 hydrocarbon and a tertiary phosphine hydrochlorate (Collie), furnishing an excellent 

 method for " retrograding" from quaternary to tertiary bodies. 



" When the phosphonium chloride contains several ethyl groups, then if more than 

 one of the latter is present, ethylene is always formed, e.g., 



(C 2 H 5 ) 3 (C 7 H 7 )PC1 - (C 2 H 5 ) 2 (C 7 H 7 )P.HC1 + C 2 H 4 . 



But when only one ethyl group is present, then, although ethylene is still formed, two 

 decompositions occur, e.g., 



(1) 2(C 2 H 5 )(CH 3 )3PC1 = 2(C 2 H 5 )(CH 3 ) 2 P.HCH-C 2 H 4 



(2) (C 2 H 5 )(CH 3 ) 3 PC1= (CH 3 ) 3 P.HC1 + C 2 H 4 . 



If we compare the decomposition by heat of phosphonium chlorides with the 

 decomposition of any of the compound ammonium salts, it must be with the hydroxides 

 and not wth the corresponding chlorides" (CoLLiE),t e.g., 



(C 2 H 6 ) 4 PC1 =(C 2 H 5 ) 3 P.HC1 + C 2 H 4 

 (C 2 H 5 ) 4 NOH = (C 2 H 5 ) 3 N + C 2 H 4 +H 2 



(C 2 H 5 ) 3 (C 7 H 7 )P(OH) - (C 2 H 5 ) 3 PO + C 7 H 8 

 (C 2 H 5 ) 3 (CH 3 )NC1 =(C 2 H 5 ) 3 N +CH 3 C1. 



The effect of heat on phosphonium salts derived from oxy-acids is completely 

 different. In the case of the ethyl series at all events, they suffer, as a rule, at least 

 two and occasionally three different and distinct decompositions. In one of these the 

 molecule splits up into three new groups, consisting respectively of carbonic anhydride, 

 a (paraffin) hydrocarbon, and the tertiary phosphine. In the other, two hydrocarbons are 

 formed, namely, an define and a paraffin, in addition to carbonic anhydride and the 

 tertiary phosphine. Whilst in the third, a totally different change occurs, in which 

 only two products are formed, namely, the oxide of the tertiary phosphine and a ketone, 



(1) Et 3 P<^ R =Et 3 P + C0 2 +C 2 H 5 R. 



(2) Et 3 P<^^ = Et 3 P+C0 2 +C 2 H 4 + RH. 



(3) Et 3 P<g^, R = Et 3 PO + C 2 H 5 .CO.R . 



It is possible, if not indeed probable, that the third reaction occurs subsequently to 

 the first, and that it really depends upon the reducing action of the triethylphosphine 



* Letts and Collie, (1) these Transactions, xxx. part 1, p. 213; and (2) Phil. Mag., August 1886. 

 t Collie, (1) Chem. Soc. Jour., 1888, p. 636; aud (2) Ibid., p. 714. 



