Semiempirical studies on the transition structure of the Baeyer and Villiger rearrangement. The reaction of acetone with alkyl and aryl peracids

The mechanism of Baeyer-Villiger reaction with substituted peracids is anal yzed by determining with semiempirical (AM1 and PM3) methods, the Mulliken charges, structures, energies, and the evolution of bond orders. A signific ant correlation was found between the bond order and the activation energy as well as with the charge and the activation energy. Elliptical coordinate s were extensively used, finding correlation between the energy of activati on and the parallel, antisymmetric coordinates, and eccentricity. The latte r was also correlated with the shift of bond order. The geometries of the C riegee intermediate, the methyl group migration transition state structure (TSs), and the product were found and optimized. As in our previous work, w e find that the topology of the TSs is invariant. By using elliptic coordin ates we can also observe that the atoms constituting three reactive circuit s are found on ellipsoidal surfaces where the reactive centers are the foci . The relationship between the energy of activation and the Hammett electro nic constant of each of the substituents is presented. (C) 2000 Elsevier Sc ience B.V. All rights reserved.