| Abstract
| - Oxidation of substituted alkenes by permanganate follows a (3 + 2) cycloaddition mechanism. DFTcalculations (Becke3LYP/6-31G(d)) strongly favor the (3 + 2) pathway against a (2 + 2) pathwaythat proceeds through a metallaoxetane. The difference in free activation energy between the twopathways is around 40 to 45 kcal/mol for the nine compounds covered. The results for the (3 + 2)cycloaddition mechanism are in agreement with experimentally observed kinetic data reportedearlier. Symmetric transition states are calculated for alkenes with at least one CH2 group betweenthe double bond and the acid group, while all others are unsymmetrical due to the repulsion betweenthe permanganate oxygens and the carboxylic oxygens. Steric bulk, introduced by the number andposition of substituents at the double bond, has no significant effect on the activation energies. Ahigher level of theory (Becke3LYP/6-311G(d,p)) leads to a reduction of the rmsd betweenexperimental and calculated values, but has little influence on the calculated geometries.
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