Can electric fields drive chemistry for an aqueous microdroplet?

Reaction rates of common organic reactions have been reported to increase by one to six orders of magnitude in aqueous microdroplets compared to bulk solution, but the reasons for the rate acceleration are poorly understood. Using a coarse-grained electron model that describes structural organization and electron densities for water droplets without the expense of ab initio methods, we investigate the electric field distributions at the air-water interface to understand the origin of surface reactivity. We find that electric field alignments along free O-H bonds at the surface are similar to 16 MV/cm larger on average than that found for O-H bonds in the interior of the water droplet. Furthermore, electric field distributions can be an order of magnitude larger than the average due to non-linear coupling of intramolecular solvent polarization with intermolecular solvent modes which may contribute to even greater surface reactivity for weakening or breaking chemical bonds at the droplet surface.

Automated summary

Reaction rates of common organic reactions can significantly increase by several orders of magnitude in aqueous microdroplets compared to bulk solution. However, the reasons for this rate acceleration are still poorly understood. By studying the electric field distributions at the air-water interface, it has been found that the electric field alignments along free O-H bonds at the surface are on average around 16 MV/cm larger than those in the interior of the water droplet. This difference in electric field distribution may contribute to the enhanced surface reactivity observed in microdroplets.