FUNDAMENTAL CONCEPTIONS 211 



pounds belonging to classes 1 and 3 contain a small and relatively 

 varying per cent of active particles with one or more carbon atoms 

 temporarily in an active or trivalent condition; the same is true 

 of compounds containing hydrogen bound to carbon-paraffines, 

 C n H Jn+1 H, benzene derivatives, etc. The isolation of compounds 

 containing trivalent carbon as such, I believe, however, to be an impos- 

 sibility. Gomberg's triphenylmethyl, for instance, has recently been 

 proved by him and others to be a bimolecular aggregate C 38 H 3 o, 

 identical with hexaphenylethane which, however, like the above- 

 mentioned compounds, contains a very small percentage of active 

 triphenylmethyl, (C 6 H 5 ) 3 =C , particles in dynamic equilibrium 

 with the bimolecular aggregate. 



We are now in a position to consider the evidence showing that 

 methylene and its homologues play a great role in many of the 

 fundamental reactions of organic chemistry which have hitherto 

 been explained on the basis of substitution. 



III. On the Reactions of the Monatomic Alcohols and the Alkylhaloids 



The experiments which first suggest themselves as a means of 

 isolating methylene and its homologues are, (1) dissociation of de- 

 fines as ethylene : 



CH 2 <=2H 2 C = ,/? butylene, 



CH S CH: CH-CH 3 <=2CH 3 CH etc. 



Since ethylene gives hydrogen and acetylene by heat and the higher 

 olefines also decompose with evolution of hydrogen, there was little 

 prospect of success by experiments in this direction. (2) Dehydration 

 of the monatomic alcohols, C n H 2n+1 OH, or removal of halogen 

 hydride from the alkylhalides, C n H 2n+1 X; naturally only primary and 



R 



secondary derivatives, RCH 2 X and ^ CHX [X = OH Cl Br or I], 



R' 



and not tertiary compounds, R 3 = C X, can yield methylene and 

 its homologues. Furthermore since many of the alcohols and alkyl- 

 halides containing more than one carbon atom in the molecule are 

 known to give olefines by dissociation, dehydration, or treatment 

 with alcoholic potash respectively, the conclusion might naturally 

 at first be drawn that only a direct olefine dissociation existed in 

 these cases. From a purely theoretical standpoint, however, it is 

 clear that a primary or secondary alkylhalide or a corresponding 

 alcohol with more than one carbon atom in the molecule may disso- 



