Decomposition and Kinetics of CH2(OH)C(O•)(CH3)CH2Cl Radical in the Atmosphere: A Quantum Mechanical Study

Abstract

We have presented the quantum mechanical calculations of the decomposition pathways of 1, 2-hydroxy alkoxy radical i.e. CH₂(OH)C(O^•)(CH₃)CH₂Cl radical. This radical species is formed from the successive reactions with O₂ molecule and NO_x or HO₂ radicals with the most stable primary oxidation product of 3-chloro-2-methyl-1-propene and OH radical reaction. Geometry optimization and frequency calculations of all the stable species including transition states in the three possible C-C bond scission pathways (i.e. C-CH₃, C-CH₂Cl and C-CH₂OH) of CH₂(OH)C(O•)(CH₃)CH₂Cl radical are performed at M06-2X/6-31+G(d,p) level of theory. We have further performed single point energy calculations of all the optimized species at the higher level of CCSD(T) method along with cc-pVTZ triple-zeta basis set. The rate constants for the various decomposition reactions are evaluated using Canonical Transition State Theory (CTST) within the temperature range of 250−400 K. Rate constants for C–C bond scissions of C-CH₃, C-CH₂Cl and C-CH₂OH of the 1, 2-hydroxy alkoxy radical are found to be 4.17 × 10¹, 1.59 × 10³ and 1.38 × 10⁹ s^-1 respectively at 298 K and 1 atm. The energetic and kinetics results suggest that C–CH₂OH bond scission of titled radical is more dominant than other decomposition channels.