ISOMERIC CHANGE 

 PART II. THE MECHANISM OF ISOMERIC CHANGE 1 



By T. MARTIN LOWRY, D.Sc. 



Lecturer in Physical Chemistry and Instructor in Crystallography at the 

 Central Technical College, London 



It has long been recognised that many isomeric changes can 

 only proceed under specific conditions and that a definite 

 machinery is necessary to effect the rearrangement of the 

 various atoms in the molecule. By the work of Butlerow, 

 between 1867 and 1877, it was, for instance, clearly proved 

 that isomeric change amongst the alcohols depends on the 

 formation of an intermediate olefine, that isomeric change 

 amongst the defines depends on the formation of an inter- 

 mediate alcohol (or alkyl sulphate), and finally that these 

 changes proceed reversibly only in contact with sulphuric acid 

 of suitable strength. 



In the present article it is proposed to describe the evidence 

 which justifies the view that a similar mechanism is necessary 

 in all cases of isomeric change, and to discuss the action of 

 the catalyst and the mechanism of the action in a number 

 of typical changes, including the racemisation or inversion 

 of optically-active compounds. 



A. The Laws controlling Chemical Change 



Before referring specifically to isomeric change it will be 

 desirable to prepare the way by a brief discussion of the 

 mechanism of chemical change in general. In this matter the 

 experiments of Dixon and of Baker on the catalytic action of 

 moisture in gaseous interactions are of supreme importance, 

 as the conditions are of the very simplest and on this account 

 are admirably adapted for the investigation of the fundamental 

 laws. It is, perhaps, an unconscious tribute to the influence 

 of the German school of physical chemistry, or perhaps of the 



1 The previous article, " Isomeric Change, Part I. Historical Development of 

 the Theory," appeared in Science Progress, 1909, 3. 616-37. 



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