Reactions of H₃O⁺ with a number of bromine containing hydrogen and fully halogenated halocarbons

The thermal bimolecular rate coefficients and product ion branching ratios for the reactions of H3O+ with the bromine containing molecules CH3Br, CH2Br2, CH2FBr, CHF2Br, CHFBr2, CH2BrCl, CHBrCl2, CHBr2Cl, CH3CH2Br, CH2BrCH2Cl, CH2BrCH2Br, CF3CF2Br and CF2BrCF2Br at 300 K are reported. H3O+ reacts with an experimental rate coefficient (k(exp)) close to the collisional value (k(C) approximate to 10(-9) cm(3) molecule(-1) s(-1)) with CHFBr2, CHBrCl2, CHBr2Cl, CH2BrCH2Cl, and CH2BrCH2Br, at a decreased efficiency with CH3CH2Br (k(exp)/k(C) approximate to 0.3). The other neutral reactant molecules, CH3Br, CH2FBr, CHF2Br, CF3CF2Br, and CF2BrCF2Br react through a three-body associative process. There is no observable reaction with CH2Br2 and CH2BrCl. Mechanistic arguments are given that go some way to explaining the observed range in both reactivity and reaction pathways. (C) 2002 Elsevier Science B.V. All rights reserved.