Catalyst-Free Radical Reaction Driven by Interfacial Electric Fields in Organic Microdroplets under Ambient Conditions

Inspired by the demonstrated ability of static electric fields to drive chemical reactions, we demonstrate that intrinsic interfacial electric fields at organic microdroplet interfaces can drive radical reactions without external catalysts or applied potentials. Using pyridine-dimethyl sulfoxide (DMSO) microdroplets as a model system, we directly confirm the presence of strong interfacial electric fields through induced charge accumulation measurements and Raman spectroscopy. These fields efficiently drive the catalyst-free methylation of pyridine to 2-methylpyridine (21.1 μM/h) under ambient conditions. Mechanistic investigations reveal that the reaction is initiated by the electric-field-induced generation of hydrogen radicals from pyridine, which then triggers an oxygen-mediated cascade to produce methyl radicals from DMSO for the subsequent methylation. This pathway is unequivocally supported by a combination of isotopic labeling, spin-trapping experiments, and density functional theory (DFT) calculations. The successful application of this strategy to other substrates underscores the broad potential of harnessing interfacial electric fields in organic microdroplets for catalyst-free radical-mediated organic reactions.