Quantum chemical study on the reaction mechanism and kinetics of Cl-initiated oxidation of methyl n-propyl ether

Oxidation of methyl n-propyl ether (CH3CH2CH2OCH3) molecule initiated by Cl atoms has been carried out using a dual level of quantum chemical investigation to understand the mechanistic pathways and kinetics of the H-atom abstraction reaction. Firstly, geometry optimization and frequency calculations for all the species are performed using BHandHLYP/6-311++G(d, p) level of theory at 298 K, and energetic calculations are further refined using CCSD(T) method with the same basis set to explore all stationary points on potential energy profile. We have observed from the energy profile that H-atom abstraction from -OCH2 group of CH3CH2CH2OCH3 is the kinetically predominant pathway. The reported bond dissociation energy for the dominant path is found to be in good agreement with the experimentally determined value. Further, standard Gibbs free energies (Delta G degrees(298)) and standard enthalpies (Delta H degrees(298)) analyses also indicate that the H-atom abstraction from -OCH2 group of CH3CH2CH2OCH3 is thermodynamically more favourable than other abstraction channels. The rate coefficients are also reported using canonical transition state theory, which is found to be in good agreement with the experimental data. The atmospheric lifetime of title molecule is also calculated.