Controlling reaction rate of phase transfer hydrogenation of acetophenone by application of low external electric field

The controllable mass transfer and reaction rate for phase transfer hydrogenation of acetophenone across a well‐defined boundary were investigated. The effect of solvent was found important and 1‐butanol exhibited the best performance among the five investigated homologous alcohol solvents, consistent with its higher solubility in water and greater dielectric constant. Initial reaction rates increased with increasing electric potential, consistent with enhanced mass transfer across the aqueous/organic boundary. At longer reaction times, deactivation was apparent. It correlated with increasing voltage and is ascribed to lower equilibrium concentration of reactive species at the interface. External control over reaction rate was demonstrated by switching the applied electric potential over the course of the reaction. Effects of external electric field on enantioselectivity were also explored with reversal field direction. The changes correlate with catalyst decomposition.