BENZYL PHOSPHINES AND THEIR DERIVATIVES. 537 



upon the carbonic anhydride, at the high temperature at which the decomposition usually 

 occurs, whereby carbonic oxide is liberated, which combines with the hydrocarbon radical 

 in statu nascendi, forming a ketone : — 



Et 3 P+C0 2 +(Et)+(R) = Et 3 PO + EtCOR 

 (or Et 3 P+(OCO-R) + (Et) = Et 3 PO + EtCOR). 



If we merely consider the third kind of decomposition alone, it appears to be, to a 

 certain extent, analogous to the decomposition which a sulphine compound suffers when 

 heated, the difference depending on the greater attraction which phosphorus has for 

 oxygen, compared with that of sulphur for the same element. In both cases a hydrocarbon 

 group is detached from the molecule, and also the residue of the acid, but while with the 

 sulphur compounds these two simply combine (forming a compound ether), and leave a 

 hydrocarbon sulphide, in the case of the phosphonium salt the acid residue is reduced by 

 the tertiary phosphine, and the group thus left combines with the hydrocarbon radical, 

 forming a ketone. 



Thus— 



Q t OCR =Et 2 S + EtOOCR. 



Et 2 S< 



Et 3 P<g : Q CR =Et 3 PO + EtOCR 



A result of this kind is in perfect harmony with the views already expressed by 

 Crum Brown and Letts* regarding the analogies and differences existing between 

 phosphorus and sulphur and their compounds. 



When the phosphonium salts contain ethylene they suffer a different decomposition 

 under the influence of heat ; at least this has been ascertained to be the case with the 

 bromide of bromo-ethylene-triethylphosphonium, and the bromide of hydroxy-ethylene- 

 triethyl phosphonium, which decompose as follows :t — 



C 2 H 4\pJq H ) B r =HBr+(C 2 H 3 )(C 2 H 5 ) 3 PBr 



and also in that of the hydrate of ethylene-hexethyl diphosphonium, which decomposes 

 according to the equation, 



Masson and Kirkland J have studied the action of bromine and chlorine on the salts of 

 tetrethyl phosphonium, the results showing a very close similarity between the poly-haloid 

 derivatives of tetrethyl phosphonium and those of trimethyl sulphine and of tetramethyl 

 ammonium previously described by Dobbin and Masson. § The tendency to form solid 



* Crum Brown and Letts, these Transactions, xxviii. p. 371 ; Letts, these Transactions, xxx. p. 285. 



t Hofmann. t Masson and Kirkland, Chem. Soc. Jour., 1889 (Trans.), p. 126. 



§ Dobbin and Masson, Chem. Soc. Jour., 1885 (Trans.), p. 56, and 1886, p. 846. 



