Pathways for the OH + Cl<inf>2</inf> → HOCl + Cl and HOCl + Cl → HCl + ClO Reactions

Wang, Hongyan and Qiu, Yudong and Czakó, Gábor and Schaefer, Henry F. (2015) Pathways for the OH + Cl<inf>2</inf> → HOCl + Cl and HOCl + Cl → HCl + ClO Reactions. JOURNAL OF PHYSICAL CHEMISTRY A, 119 (28). pp. 7802-7809. ISSN 1089-5639

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Abstract

High level coupled-cluster theory, with spin-orbit coupling evaluated via the Breit-Pauli operator in the interacting-states approach, is used to investigate the OH radical reaction with Cl<inf>2</inf> and the subsequent reaction HOCl + Cl. The entrance complex, transition state, and exit complex for both reactions have been determined using the CCSD(T) method with correlation consistent basis sets up to cc-pV6Z. Also reported are CCSDT computations. The OH + Cl<inf>2</inf> reaction is predicted to be endothermic by 2.2 kcal/mol, compared to the best experiments, 2.0 kcal/mol. The above theoretical results include zero-point vibrational energy corrections and spin-orbit contributions. The activation energy (E<inf>a</inf>) of the OH + Cl<inf>2</inf> reaction predicted here, 2.3 kcal/mol, could be as much as 1 kcal/mol too high, but it falls among the four experimental E<inf>a</inf> values, which span the range 1.1-2.5 kcal/mol. The exothermicity of the second reaction HOCl + Cl → HCl + ClO is 8.4 kcal/mol, compared to experiment 8.7 kcal/mol. The activation energy for latter reaction is unknown experimentally, but predicted here to be large, 11.5 kcal/mol. There are currently no experiments relevant to the theoretical entrance and exit complexes predicted here. © 2015 American Chemical Society.

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