Harnessing the High Interfacial Electric Fields on Water Microdroplets to Accelerate Menshutkin Reactions

Even though it is still an emerging field, the application of a high external electric field (EEF) as a green and efficient catalyst in synthetic chemistry has recently received significant attention for the ability to deliver remarkable control of reaction selectivity and acceleration of reaction rates. Here, we extend the application of the EEF to Menshutkin reactions by taking advantage of the spontaneous high electric field at the air-water interfaces of sprayed water microdroplets. Experimentally, a series of Menshutkin reactions were accelerated by 7 orders of magnitude. Theoretically, both density functional theory calculations and ab initio molecular dynamics simulations predict that the reaction barrier decreases significantly in the presence of oriented external electric fields, thereby supporting the notion that the electric fields in the water droplets are responsible for the catalysis. In addition, the ordered solvent and reactant molecules oriented by the electric field alleviate the steric effect of solvents and increase the successful collision rates, thus facilitating faster nucleophilic attack. The success of Menshutkin reactions in this study showcases the great potential of microdroplet chemistry for green synthesis.