Kinetic and mechanistic study of the reactions of OH with IBr and HOI

The kinetics and mechanism of the reactions of OH radicals with IBr and HOI have been studied using the mass spectrometric discharge-flow method at 320 K and at a total pressure of 1 Torr of Helium. The rate constant of the reaction OH + IBr → products (1) was measured under pseudo-first order conditions either in excess of IBr or in excess of OH radicals: k1 = (1.4 ± 0.4) × 10−10 cm3 molecule−1 s−1. Both HOI and HOBr were detected as products of reaction (1) and the branching ratios 0.84 ± 0.07 and 0.14 ± 0.05, respectively, were found for the channels forming these species. For the reaction OH + HOI → products (2) the total rate constant was determined from the kinetics of HOI consumption in excess of OH radicals: k2 = (5.0 ± 1.2) × 10−12 cm3 molecule−1 s−1.