Less common patterns of reduction of some oximes

Most oximes are reduced in a single, pH-dependent, four-electron wave, in which an amine is formed. Examples of reduction of some oximes, which differ from this general pattern, are reported. These different behaviors can be caused by changes in acid-base equilibria and in the rate of their establishment. Such changes can result from the role of strongly electron-withdrawing substituents, such as the cyano group. Alternatively the reduction pattern can be changed by a covalent hydration of the C=N bond. This has been observed for compounds bearing a CF3 group adjacent to the oximino group. Finally, a different reduction pattern can result from interposed acid-base reactions. The difference in such reactions cause different reduction patterns of two isomeric monoximes of 1-phenyl-1,2-propanedione