212 CHEMISTRY 



ciate with loss of halogen hydride or water in two possible ways: 

 it may undergo (1) methylene dissociation, as 



X 



R CH 2 CH <=^R 



H 

 R H R 



and C <= 



R' X R' ' 



or (2) olefine dissociation, as R'CH 2 - CH 2 X<=R-CH-CH 2 +HX, 



, , ' ' 



and CH 3 CH 2 -CHX-CH 3 <^CH 3 CH-CH-CH 3 



and CH 3 CH 2 -CH-CH 2 



or both kinds of dissociation may take place simultaneously. A 

 third kind of dissociation, where the hydrogen atom does not come 

 from the atom containing the X or from a carbon atom adjacent to it, 

 is also possible, and at times important, but it need not be considered 

 in this connection. 



An exhaustive study of the primary and secondary alcohols and 

 alkylhalides covering a period of nine years has proved very con- 

 clusively that these substances undergo methylene dissociation 

 only. Preliminary experiments with alcohols and alkylhalides where 



H 



no olefine dissociation is possible, i. e., in the methane, H 2 C^ 



X 

 H H 



toluene, C 6 H 5 CH , diphenylmethane (C 6 H 5 ) 2 : C , acetone 



X X 



H H 



and acetophenone, CH 3 CO CH and C 6 H 5 COCH , malonic 



X X 



X CN H 



and cyanacetic ether series (COOR) 2 C and ^C , have 



H COOR X 



proved that all these compounds have very low dissociation-points 

 never over 300 in the aromatic nor with few exceptions in the 

 aliphatic series. Nevertheless, it was found impossible to isolate in 



