Dual-Level Direct Dynamics of the Hydroxyl Radical Reaction with Ethane and Haloethanes: Toward a General Reaction Parameter Method

The dynamics of hydroxyl radical reactions with ethane, fluoroethane, and chloroethane have been examined in terms of variational transition state theory augmented with multidimensional semiclassical tunneling corrections. Differences in reactivity for hydrogen abstraction from both the primary and the secondary carbon atoms are examined in terms of energetic and entropic effects on the location of the dynamical bottleneck. Interpolated variational transition state theory is used to calculate reaction rate constants at the [G2(MP2)//MP2/6-31G(d,p)]/SCT level of theory. A vibrational-mode correlation analysis is performed; i.e., the character of the vibrational modes are identified as a function of the reaction coordinate and a statistical diabatic model is used to provide qualitative analysis of a possible vibrational-state specific chemistry for this reaction. A significant enhancement of the reaction rate is predicted for the excitation of the pertinent C−H stretching mode of the reactant hydrocarbon mo...