Theoretical investigation on the kinetics and branching ratio of the gas phase reaction of sevoflurane with Cl atom.

The present work deals with the theoretical investigation on the Cl initiated H-atom abstraction reaction of sevoflurane, (CF3)2CHOCH2F. 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 –CH2F end of the sevoflurane. The rate constant of the dominant path is found to be 1.13 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹. This is in excellent agreement with the reported experimental rate constant of 1.10 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ obtained by relative rate method using FTIR/Smog chamber and LP/LIF techniques.