| Abstract
| - Ab initio and semiempirical calculations have beenperformed on the reaction mechanism of the Baeyer−Villiger reaction of acetone and performic acid. They focus, at therate-limiting step (RLS), on the structures,energies, Mulliken charges, and what we refer to as evolution of thebond orders. The geometries of theCriegee intermediate, the methyl group migration transition statestructure (TSs), and the product were foundand optimized with the HF/ 4-21G, the HF/4-31G, and the HF/6-31G**basis sets of double-ζ quality in theab initio methodology. AM1, PM3, and MNDO were used inthe semiempirical calculations. The correlationenergies were also evaluated at the MP2/6-31G**//HF/4-31G andMP2/6-31G** level of theory. A discussiondealing with the nature of the transition state structure (TSs) and itsdetermination is presented, observingthat irrespective of the method of calculation, the topology of the TSsand the general orientation of thetransition vectors are invariant. From the calculations invacuo, by using novel methodology, we findtworeactive cycles: a central one, where the oxygen bonds break in closesynchronicity with the methyl groupmigration, and a secondary one, where a proton is transferred.This proton seems to have protected thecarbonyl oxygen from the attack of the methyl group. Scanning themovement of the proton, we can observethe effect that it produces on the atoms belonging to the reactivecycles and, interestingly, the lack of effecton those that do not belong to it. Finally, by using ellipticcoordinates, we see that the atoms constitutingboth of the reactive cycles are found on ellipsoidal surfaces where thereactive centers are the foci.
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