Quantum Chemistry\nStudy on Cl-Initiated Reactions\nof 2‑Chloropropane and 2‑Methylpropanoyl Halogen (Cl,\nBr, F): Mechanism, Kinetics, and Atmospheric Implications

Halogenated volatile organic compounds (HVOCs) pose significant\nbioaccumulative and toxicological risks, necessitating effective strategies\nfor their removal. Here, we show, through a computational study employing\ndensity functional theory and coupled cluster methods, the detailed\nmechanism and kinetic properties of Cl-initiated degradation reactions\nof 2-chloropropane (2-CP, (CH<sub>3</sub>)<sub>2</sub>CHCl) and 2-methylpropanoyl\nhalide ((CH<sub>3</sub>)<sub>2</sub>CHCOX, X = Cl, Br, F). The reaction\nrate constants of all the channels were calculated by the canonical\nvariational transition state theory (CVT) with the correction of the\nsmall curvature tunneling effect (SCT) at 200–1000 K. The subsequent\ntransformation pathways of the major radical products of (CH<sub>3</sub>)<sub>2</sub>CHCl and (CH<sub>3</sub>)<sub>2</sub>CHCOCl in the presence\nof O<sub>2</sub>, NO, and HO<sub>2</sub> radical were investigated.\nThe results elucidate the reaction pathways and rate constants, which\nare in excellent agreement with the experimental data at 296 K. We\nfurther explore the atmospheric implications of these reactions by\nassessing the atmospheric lifetime (τ) and ozone depletion potential\n(ODP). Additionally, we delve into the aquatic toxicity and bioaccumulation\npotential of the reactants and their transformation products. This\nstudy not only advances our knowledge of the atmospheric fate of halogenated\nhydrocarbons but also underscores the importance of considering the\nenvironmental and toxicological impacts in the development of HVOC\nmitigation strategies.