ISOMERIC CHANGE 217 



In each of these cases the action is held back, not only by the 

 necessity of a catalyst, but by the much greater difficulty of 

 discharging the electrolyte through electrodes which are almost 

 entirely devoid of conducting properties. 



Most of the isomeric changes that have been observed 

 amongst organic compounds are actions of the same type as 

 the bromination of ethylene or the nitration of benzene — these 

 are considered in section B as " Isomeric Changes of the First 

 Group"; but many examples are also known of compounds 

 which can act as electrolytes and undergo isomeric change 

 with the readiness characteristic of compounds of this class — 

 these are considered in section C as " Isomeric Changes of 

 the Second Group." Changes of both types involving the 

 racemisation of optically active compounds are discussed in 

 section D. 



B. Isomeric Changes of the First Group 



The isomeric changes observed in typical non-electrolytes, 

 such as the olefines, proceed as a rule quite slowly, and only 

 after the deliberate addition of some well-defined catalytic agent. 

 They are therefore devoid of the qualities which confer such 

 an elusive character on the more facile isomeric changes of 

 section C ; as a result, the history of their investigation has 

 been pleasantly free from speculative theories and bewildering 

 nomenclature. The changes that have been most fully studied 

 are those involving the transference of halogens, and of nitro, 

 sulphonic and hydroxyl groups ; the compounds containing 

 sulphonic groups are, of course, electrolytes, but as electrolysis 

 results only in the separation of a hydrogen atom and not of 

 the sulphonic group, the transference of this group takes place 

 under conditions precisely similar to those which govern 

 isomeric change in non-electrolytes. It is shown below that 

 all these changes can be accounted for by means of an 

 electrolytic theory, the catalyst acting as the electrolyte, and 

 the organic compound as depolariser in the electric circuit. 



(a) Transference of a Halogen Atom. — An excellent example 

 of the conditions governing the transference of a halogen atom 

 is found in the behaviour of camphor on bromination. At 

 ordinary temperatures and pressures {eg. on heating camphor 

 in a flask on a water-bath and running in one or two mole- 



