Carbonium ions cinnamyl

In aprotic solvents, the allylic carbonium ion and carboxylic acid molecule produced by acid-catalyzed heterolysis of an allylic ester may recombine to form the starting material and its allylic isomer. Kinetic studies show that a-phenylallyl p-nitrobenzoate undergoes concurrent uncatalyzed and p-nitro-benzoic acid-catalyzed isomerization to cinnamyl benzoate in chlorobenzene solutions containing p-nitrobenzoic acid . Similarly, benzoic acid catalyzes the isomerization of a-phenylallyl benzoate in chlorobenzene. When this reaction was carried out using 0-labeled benzoic acid, appeared in both the starting material and its allylic isomer under the conditions used, only about a quarter of the isomerization reaction is intramolecular. 

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