Temperature Dependence of the Reaction HCl + OH → Cl + H ₂ O between 140 and 1100 K

Temperature dependence of the molecule-radical reaction HCl + OH → Cl + H ₂ O at temperatures between 140 and 1100 K is studied using a quasiclassical trajectory method. Potential energy surfaces are formulated using pair-wise additive two-body, nonadditive three-body, and four-body analytic forms and long-range interactions. At temperatures above 300 K, the reaction occurs by direct collisions and the calculated rate constant fits the Arrhenius equation k _dir = 4.85 × 10 ⁻¹² exp.(−631 ± 10/T) cm ³ /molecule/s. At temperatures below 300 K, the reaction is driven by an attractive potential and occurs through the formation of a ClH…OH collision complex, which is sufficiently long-lived to enhance quantum mechanical tunneling of the H atoms. The sum of the direct and complex-mode reaction rates effectively describes the reaction occurring at temperatures in the 140–1100 K temperature range.