Rearrangements involving the phenonium ion: A theoretical investigation

Rearrangements involving the phenonium ion were investigated by means of a B3LYP/6-311G-(d,p) study in which the effect of solvent has been incorporat ed by using a PCM solvation model. A rationalization of the whole set of ex perimental facts reported both in the gas phase and in solution was possibl e thanks to the characterization of protonated benzocyclobutene as a minimu m energy structure and, particularly, to the important preferential stabili zation in solution of the TS for the isomerization of the phenonium ion to the alpha -methylbenzyl ion, which reduces the Gibbs energy barrier of 26.6 kcal/mol for this process in the gas phase to a more accessible one of 18. 7 kcal/mol in solution.