ISOMERIC CHANGE 



235 



whilst in the case of ether the absence of any catalytic action 

 may be accounted for by the fact that even if an additive 

 compound were formed it could not act as an intermediate 

 stage in the interconversion of the two isomerides. There can 

 therefore be little doubt that these catalysts act in the manner 

 suggested, their addition to the nitrocamphor molecule being 

 effected as in previous cases by an electrolytic process. 



It is conceivable that in this operation the nitro-compound 

 might act as electrolyte and the catalyst as depolariser, but 

 this does not appear to be probable in view of the fact that it 

 is the catalyst and not the nitro-compound that is split up in 

 the formation of the additive compound. A more likely ex- 

 planation of the extreme facility of the isomeric change in sub- 

 stances of this type is that the separation of the hydrogen in 

 an ionic form and its addition to and removal from the molecule 

 as H.C1, H.OH, H . OC 2 H 5 or H . O . CO . CH 3 , although 

 not directly related to one another as cause and effect, are 

 cognate properties which are dependent on similar circum- 

 stances, and are affected in the same way by the presence or 

 absence of negative groups. 



The view that these facile isomeric changes are due to the 

 addition and removal of water, or some similar substance,, 

 receives strong support from the behaviour of sugars, such as 

 glucose and galactose, which undergo isomeric change very 

 readily in aqueous solutions, rather less readily in alcohol, and 

 are very susceptible to the influence of alkaline catalysts. 

 There is the strongest possible evidence l that the conversion 

 of a- into /3-glucose takes place through the formation of an 

 intermediate hydrate, 



H 



OH 



HO 



H 



1 See Trans. Chem. Soc. 1903, 83, 1314-16 ; 1904, 85, 1565. 



