Charge Oscillation in the Homolysis of MeX Derivatives

Ab initio electronic structure methods are used to show that, in the (barrierless) homolytic dissociation of the CH₃X system (X = an atom or group more electronegative than CH₃) going from equilibrium geometry to products (CH₃^• + X^•), the charge on CH₃ first increases and then decreases to zero. This result, which can be rationalized on the basis of simple models, violates the common assumption that the character of intermediates along a reaction path is bound by the properties of reactants and products. The implications of this new conclusion to kinetic/thermodynamic data relationships in chemical reactions are discussed.