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The present work deals with the theoretical investigation on the Cl initiated H-atom abstraction reaction of sevoflurane, (CF)CHOCHF. A dual-level procedure has been adopted for studying the kinetics of the reaction. Geometrical optimization and frequency calculation were performed at DFT(BHandHLYP)/6-311G(d,p) while single-point energy calculation was made at CCSD(T)/6-311G(d,p) level of theory. The intrinsic reaction coordinate (IRC) calculation has also been performed to confirm the smooth transition from the reactant to product through the respective transition state. The rate constants were calculated using conventional transition state theory (TST). It has been found that 99 % of the reaction proceeded via the H-atom abstraction from the -CHF end of the sevoflurane. The rate constant of the dominant path is found to be 1.13 × 10 cm molecule s. This is in excellent agreement with the reported experimental rate constant of 1.10 × 10 cm molecule s obtained by relative rate method using FTIR/Smog chamber and LP/LIF techniques. [ABSTRACT FROM AUTHOR]

The kinetics of hydrogen atom abstraction reactions of HFE-227pc by OH and Cl was studied by ab initio method. The structural optimization and frequency calculation of the titled compound and the species formed during the abstraction reactions were performed with density functional theory using hybrid meta density functional MPWB1K with 6-31 + G(d,p) basis set. The energy of the species was further refined by making a single point energy calculation at G3B3 level of theory. The standard enthalpies of formation of reactant and the radical formed after H-atom abstraction was calculated using isodesmic method. The rate constants of abstraction reactions were calculated using Conventional Transition State Theory (CTST) and were found to be 1.5 × 10 and 0.53 × 10 cmmolecule s for OH and Cl respectively. The calculated value for the abstraction by OH is close to the experimental value of 2.26 × 10 cmmolecule s whereas the same for Cl is found to be about five times lower than that of 2.70 × 10 cmmolecule s. The theoretical studies yielded the enthalpies of formation and the rate constants that are vital in determining the lifetime of HFE-227pc. [ABSTRACT FROM AUTHOR]