Thermodynamic and kinetic studies of hydroxyl radical reaction with bromine oxide using density functional theory

Abstract

Thermodynamic properties such as enthalpies, Gibb’s free energies, entropies of BrO+OH reaction and rate coefficients were computed using density functional theory, viz. B3LYP/6-311G(2df,2pd) and mPW1PW91/6-311G(2df,2pd) level of theories. Geometries of reactants, intermediates, transitions states and products were optimized using these theories. Twelve different transitions states were identified using both the theories and confirmed by intrinsic reaction coordinate (IRC) calculations. Reaction mechanism of BrO+OH was explored using two reaction paths namely channel 1 (producing HO2+Br) and channel 2 (producing HBr+O2).Reaction channel 2 is found to be four times faster than reaction channel 1. The rate coefficient for the title reaction was computed to be k=(1.81±0.17)×10−13[exp (1532±25)/T]cm3molecule−1s−1 in the temperature range of 200 and 400K using B3LYP/6-311G(2df,2pd) level of theory. Theoretically computed enthalpy of the reaction and rate coefficients using B3LYP/6-311G(2df,2pd) level of theory were found to be in good agreement with the experimentally measured ones.