Oxotropic isomerizations of allylic compounds

Allylic alcohols, esters, and ethers undergo acid-catalyzed isomerizations, and allylic alcohols and ethers isomerize at appreciable rates only in the presence of acids. The migrating groups in these reactions are uncharged molecules derived from the oxonium ion conjugate acids of the starting materials. For this reason, and because they are mechanistically related to anionotropic isomerizations, Braude named these reactions oxotropic rearrangements. 

A number of mechanistic criteria, most of which involve kinetic data, show that these reactions generally involve dissociation of the conjugate acid of the starting material to an allylic carbonium ion and a water, carboxylic acid, or alcohol molecule, followed by recombination of the carbonium ion with an uncharged molecule from its solvation shell, viz  

The kinetic data which lead to this conclusion are summarized in the discussion which follows. 

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