B.— CHEMISTRY 



49 



transformation is probably the attachment of the oxygen atom (or its 

 representative in an intermediate product) to this carbon atom. If this 

 is so, then the consequent displacement of the nitrogen atom must 

 inevitably occur in a direction away from the oxygen atom, that is, in the 

 direction that leads to iraw^-migration. 



In any case, the passage of the nitrogen atom across the line of closest 



Oxime. 



Cis-migration 



TraMs-migration. 



Anilide (enolic form). 

 Fig. 7. 



approach of the oxygen atom to the central carbon atom, which is required 

 for m-migration, must seem exceedingly unlikely. 



This more concrete way of looking at the Beckmann transformation 

 enables us to see, I think, very clearly that the c?^-interchange of groups, 

 instead of being an assumption that could be taken for granted, was in 

 fact a highly improbable hypothesis. It indicates that the natural course 

 for the migration of groups to pursue is that which leads to a trans- 

 interchange. 



I now pass to the consideration of a question which has been of deep 

 interest to all who have reflected on stereochemical problems, the optical 



