Degradation of Isobutyl Chloride by OH Radicals and Cl Atoms: Insights into Kinetics and Atmospheric Implications

Chlorinated hydrocarbons have wide applications in the industry and are likely to be emitted to the environment, where they can influence the atmosphere. Hence, the kinetics of the degradation of isobutyl chloride (IBC) initiated by OH radicals and Cl atoms was determined both experimentally and theoretically in this work. The rate coefficients were experimentally measured from 268 to 363 K, using pulsed-laser photolysis-laser-induced fluorescence (PLP-LIF) for the reaction with OH radicals and using the relative-rate (RR) method for the reaction with Cl atoms. The room temperature rate coefficients (in cm³ molecule^-1 s^-1) for both reactions were measured to be <i>k</i>_IBC+OH^298K = (1.45 ± 0.10) × 10^-12 and <i>k</i>_IBC+Cl^298K = (5.36 ± 1.31) × 10^-11, respectively. The rate coefficients showed a dependence on temperature given by the Arrhenius equations <i>k</i>_IBC+OH^268-363K = (1.22 ± 0.32) × 10^-12 exp[(39.2 ± 81.4)/<i>T</i>] cm³ molecule^-1 s^-1 and <i>k</i>_IBC+Cl^268-363K = (1.42 ± 0.64) × 10^-11 exp[(417.2 ± 136.6)/<i>T</i>] cm³ molecule^-1 s^-1. Rate coefficients were also calculated theoretically to understand the site-specific reaction kinetics at the CCSD(T)/aug-cc-pVDZ//BHandHLYP/6-31+G(d,p) and CCSD(T)/6-311++G(d,p)//BHandHLYP/6-31+G(d,p) levels for the reaction of IBC with OH radicals and Cl atoms, respectively. Parameters were calculated to assess the impact of IBC release on the atmosphere using the obtained kinetics. The products formed in these reactions were also analyzed to comment on the detailed degradation mechanism of IBC.