Implications of Berthlot`s descriptive of associative reactions

Berthelot`s equation, k{sub {infinity}}(T) = A{sub {infinity}} exp (-Dk{sub B}T), provides a good description of the high-pressure rate coefficient for associative reactions such as CH{sub 3} + CH{sub 3}, CH{sub 3} + OH, and CH{sub 3} + H. The parameter D may be used to characterize an effective temperature-dependent barrier, {Delta}E{sub eff} = Dk{sub B}{sup 2}T{sup 2}, which is due to the internal energy, i.e. rotational and vibrational energy, or the centrifugal barrier of the associating species. The parameter A{sub {infinity}} may be identified as the rate coefficient for association when the species approach one another with zero translational and internal energy. A microcanonical rate expression is given which may be used to directly compare experimental results with theoretical calculations. In addition, this approach suggests that the Arrhenius expression for the high-pressure rate coefficient for dissociation should contain both the change of enthalpy of the reaction and this effective barrier