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.