Mechanism of F₄₃₀-Catalyzed Dehalogenations of Chloromethanes: A DFT Perspective

Rate-determining steps of the alternative mechanisms of reductive dehalogenation of chloromethanes catalyzed by the F₄₃₀ coenzyme and its truncated model have been studied theoretically at the MN15-L/def2-TZVP level of theory which yielded best agreement with the experimental data. Both, explicit and implicit solvent models were used. The energetics of these reactions and structural properties of reactants, products, their complexes, and corresponding transition state have been determined. Based on this information kinetic isotope effects (KIEs) and the corresponding "lambdas" (relation between ¹³C and ³⁷Cl KIEs) have been calculated. Two major conclusions come from these studies. First, there is a mechanistic switch with the increasing number of chlorine atoms. Second, for the studied reaction lambdas are not indicative of the mechanism.