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

The rate coefficients for the reactions of O(P-3) with CF3I (1) and CH3I (2) were measured between 213 and 364 K to be: k(1)(T) = (7.9 +/- 0.8) x 10(-12) exp[-(175 +/- 40)/T] and k(2)(T) = (1.0 +/- 0.2) x 10(-11) exp[(160 +/- 50)/T] cm(3) molecule(-1) s(-1). The rate coefficients for the reaction of O(P-3) with CD3I, (CH3)(2)CHCH2I,(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). IO, 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, Delta(f)H(o)(298.15 K)(IO) <28.8 kcal mol(-1), was obtained from an interpretation of our data.