Kinetic study of the reactions of OH and OD with HBr and DBr

The kinetics of the reactions of OH and OD radicals with HBr and DBr, OH HBr (1), OD + HBr (3), OH + DBr (4) and OD + DBr (5), have been studied by the mass spectrometric discharge-flow method at temperatures between 230 an d 360 K and at total pressure of 1 Torr of helium. The following Arrhenius expressions were obtained: k(1) approximate to k(3) = (5.3 +/- 1.2) x 10(-1 2) exp{(225 +/- 60)/T} and k(4) approximate to k(5) = (4.3 +/- 1.2) x 10(-1 2) exp{(125 +/- 80)/T} cm(3) s(-1) per molecule. The isotope exchange react ions OD + HBr --> OH + DBr (3') and OH + DBr --> OD + HBr (4') were found t o be slow and the upper limits for the rate constants of these channels wer e measured at T = 298 K: k(3') < 1 x 10(-13) and k(4') < 3 x 10(-14) cm(3) s(-1) per molecule. These results are compared with the literature experime ntal and computational data. (C) 1999 Elsevier Science S.A. All rights rese rved.