Reactions of O(³P) with alkyl iodides: Rate coefficients and reaction products

The rate coefficients for the reactions of O(³P) with CF₃I (1) and CH₃I (2) were measured between 213 and 364 K to be: k₁(T) = (7.9 ± 0.8) × 10^-12 exp[-(175 ± 40)/T] and k₂(T) = (1.0 ± 0.2) × 10^-11 exp[(160 ± 50)/T] cm³ molecule^-1 s^-1. The rate coefficients for the reaction of O(³P) with CD₃I, (CH₃)₂CHCH₂I, (CH₃)₂-CHI, CF₃CH₂I, CF₃CHFI, and CF₃CF₂I at 298 K were also measured. The yields of the IO and CF₃O products in reaction 1 at 298 K were found to be 0.83 ± 0.09 and <0.01, respectively. Product yields of reaction 2 at 298 K were measured to be IO (0.44 ± 0.04), OH (0.16 ± 0.05), H (0.07 ± 0.02), CH₃O (<0.03), and HI (<0.05). IG, OH, and CH₃O were detected via laser-induced fluorescence, O and H atoms via resonance fluorescence, and IO, CF₃O, and HI by chemical ionization mass spectrometry. The IO yield from reactions 1 and 2 showed a slight positive temperature dependence. Within our experimental error the OH yield from reaction 2 was temperature independent. An upper limit for the enthalpy of formation of IO, Δ_fH^o(298.15 K)(IO) <28.8 kcal mol^-1, was obtained from an interpretation of our data.