Solvent-assisted catalysis in the enolization of acetaldehyde radical cation

The keto-enol isomerization of neutral and ionized acetaldehyde, both isola ted and catalyzed by solvent molecules, has been studied using the B3LYP an d MP2 levels of theory. Single-point calculations at the CCSD(T) level have also been performed. The results show that ionization favors the enolizati on of acetaldehyde, both thermodynamically and kinetically. Solvent molecul es produce an important catalytic effect, especially for the methanol-solva ted system, for which the transition state of the isomerization lies below the ground-state asymptote. (C) 2001 Elsevier Science B.V. All rights reser ved.