Correlation between the OH radical reactivity of halogenated cyclobutanes and their C-H bond energies

Abstract

We have found that the reactivity trends observed for gas-phase OH radical reactions of nine halogenated cyclobutanes are strongly correlated with their C-H bond strengths. Our results have shown that a collision-theory-based kinetic equation with adjusted parameters reproduce well the rate constants of these OH radical reactions from the C-H bond dissociation enthalpies of the halogenated cyclobutanes. This kinetic equation was applied to estimate the rate constants for OH radical reactions of acyclic halogenated compounds in our previous study. Although the ring strain is likely to be related with the reactivity trends for the halogenated cyclobutanes, the best-fitted parameter values for the reactions halogenated cyclobutanes are found to be almost identical with those fitted for the reactions of acyclic counterparts. This result suggests that the effects of the ring strain should be reflected in C-H bond enthalpy values, and thus, without considering the effects of ring strain separately, we can estimate the rate constants for the OH radical reactions of acyclic halogenated compounds and those of halogenated cyclobutanes by using almost identical kinetic equation.