A gaskinetic investigation of HOBr reactions with Cl(P-2), O(P-3) and OH((2)Pi). The reaction of BrCl with OH((2)Pi)

The reactions of HOBr with atomic chlorine (1), with oxygen (2) and with hydroxyl radicals (3) have been investigated at 300 K using the discharge flow technique with mass-spectrometric detection. The rate constants based on HOBr consumption have been determined to be k(1) = (8.0 +/- 0.4). 10(-11) and k(2) = (3.1 +/- 0.2). 10(-11). For the reaction with OH radicals k(3) < 5 . 10(-13) was obtained. All rate constants are given in units cm(3) molecule(-1) s(-1). The reactions of HOBr with Cl and with O are shown to proceed via bromine abstraction with formation of BrCl and BrO, respectively. The predominant channel in the reaction of OH with BrCl was identified to be step (4a) (4a) OH + BrCl --> HOBr + Cl Based on the present kinetic investigation the heat of formation for HOBr at T = 300 K was evaluated to be Delta H-f(0)(HOBr) = -(60.22 +/- 2) kJ . mol(-1).