Temperature dependence of the rate constant for hydrogen atom reaction with Cl2−• in water by pulse radiolysis of aqueous HCl solution

•Rate constant k   (Cl2-•+H) has been determined over the range 25–75 °C.•At 25 oC k (Cl2-•+H•)= (6.1 ± 0.6)´109 M-1s-1 and Ea=13.2 ± 0.6 kJ/mol.•Ea is lower than 16.7 kJ mol−1 expected for a diffusion-controlled reaction.•The temperature dependence for k (•H+Cl2)H•+Cl2) in solution is provided.•The room temperature value for k (•H+H2O)H•+H2O) is critically evaluated.

The temperature dependence of the rate constant for the reaction of dichloride anion radical (Cl2-•) with atomic hydrogen (H•) in water up to 75 °C has been determined by pulse radiolysis of deaerated 0.1 M HCl solution. The room temperature value is (6.1±0.6)×109 M−1 s−1. The activation energy of (13.2±0.6) kJ mol−1 is less than 16.7 kJ mol−1, expected for the diffusion-controlled reaction. Based on the temperature dependence of the rate constant for the reactions H•+Cl2-• and H•+Cl2, derived in this work, and on that reported earlier (Szala-Bilnik et al., 2014) for Cl2-•+Cl2-•, we show that a value of (10±2) M−1 s−1 determined by Hartig and Getoff (1982) for k (H•+H2O) in water at 25 °C is overestimated by at least two orders of magnitude.