Ozonolysis of fluoroethene: theoretical study of unimolecular decomposition paths of primary and secondary fluorozonide.

A theoretical investigation into unimolecular decomposition paths of primary (POZF) and secondary (SOZF) fluorozonide was carried out by utilizing the multiconfigurational CASSCF/cc-pVTZ level in optimizations of the stationary points and calculations of the harmonic vibrational frequencies. The dynamical electron correlation was accounted for via the multireference CASPT2/cc-pVTZ treatment based on the zeroth-order CASSCF/cc-pVTZ reference. The CASPT2 was substituted with the CCSD(T)/6-311G(2d,2p) correction whenever the former resulted in negative activation barriers. The most favorable decomposition route of POZF is a concerted cleavage to carbonyl oxide (CO) and formyl fluoride (FF) with fragments in the anti conformation, with regard to the orientation of the terminal oxygen in the carbonyl oxide and the flourine atom of the carbonyl compound. The ratio of unimolecular rate constants calculated within the RRKM formalism suggests that the CO-FF channel of cleavage amounts to 98%, which agrees well with the upper bound of experimental esimates. The SOZF decomposition most readily takes place in a stepwise manner initiated by the O-O bond rupture. Two conformational minima are exhibited by SOZF, the O-O and H(2)C-O half-chairs. The calculated rotational constants and scaled frequencies for the O-O half-chair are in good agreement with the experimental values.