Reaction\nRate Theory for Electric Field\nCatalysis in Solution

The\napplication of an external, oriented electric field has emerged\nas an attractive technique for manipulating chemical reactions. Because\nmost applications occur in solution, a theory of electric field catalysis\nrequires treatment of the solvent, whose interaction with both the\nexternal field and the reacting species modifies the reaction energetics\nand thus the reaction rate. Here, we formulate such a transition state\ntheory using a dielectric continuum model, and we incorporate dynamical\neffects due to solvent motion via Grote–Hynes corrections.\nWe apply our theory to the Menshutkin reaction between CH<sub>3</sub>I and pyridine, which is catalyzed by polar solvents, and to the\nsymmetric S<sub>N</sub>2 reaction of F<sup>–</sup> with CH<sub>3</sub>F, which is inhibited by polar solvents. At low applied field\nstrengths when the solvent responds linearly, our theory predicts\nnear-complete quenching of electric field catalysis. However, a qualitative\ntreatment of the nonlinear response (i.e., dielectric saturation)\nshows that catalysis can be recovered at appreciable field strengths\nas solvent molecules begin to align with the applied field direction.\nThe dynamical correction to the rate constant is seen to vary nonmonotonically\nwith increasing solvent polarity due to contrasting effects of the\nscreening ability and the longitudinal relaxation time of the solvent