Some Reactions of Carbonium Ions

In cases where the pertinent configuration is a transition state rather than an intermediate, the importance of a charge-accepting structural feature will depend on the degree to which a charge is actually developed in the transition state. This means that even on electronic grounds alone it is not certain that migration aptitudes should be independent 

Another example is the migration of phenyl in preference to a-naphthyl in a similar reaction.84  

Since it is not always known to what extent the departing group is still present at the rearrangement stage of the reaction, a detailed interpretation of migration aptitudes is difficult. The examples just discussed, however, should certainly not be compared with migration aptitudes within a fully formed carbonium ion. 

The benzilic acid rearrangement, though catalyzed by hydroxide ion, probably belongs in the same category as carbonium ion rearrangements. Kinetic and isotopic exchange experiments show that there is a rapid reversible addition of hydroxide ion.841 242 

An irreversible reaction via a cyclic transition state has also been suggested 242  

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