Competitive study of the reactions Br + RBr → Br2+ R (R = CF3, C2F5)

Abstract

The overall reactions CF₃Br + HBr → CF₃H + Br₂, C₂F₅Br + HBr → C₂F₅H + Br₂ have been studied competitively over the range 195–476°C. Reaction was initiated by bromine atoms generated both thermally and photochemically. Initiation reactions are Br + CF₃Br → Br₂+ CF₃(3), Br + C₂F₅Br → Br₂+ C₂F₅(4) for which log k₃/k₄=(0.264 ± 0.075)–(2330 ± 220)/θ where θ= 2.303 RT/cal mol^–1. This confirms previous work on reactions (3) and (4) studied separately. The relevnce of the results to the determination of the bond dissociation energies D(CF₃—Br) and D(C₂F₅—Br) is discussed.