Molecular Insight into How Alcohol Catalyzes the Interfacial Chlorination of Squalene

Interfacial environments are highly sensitive to changes in composition. The addition of trace solutes or cosolvent mixtures can dramatically alter the surface composition, by altering the energetics of adsorption and solvation, or by creating nanoenvironments where chemistry is enhanced or suppressed. Prior aerosol experiments show that the addition of oxygenated spectator molecules accelerates the heterogeneous chlorination rate of squalene without altering the mechanism. Using molecular dynamics simulations and kinetic models, we find that long-chain alcohols are enriched in a subsurface layer and enhance reactivity both at the interface and in the bulk. The bulk reaction rate increases by an order of magnitude relative to pure squalene, while the interfacial rate is accelerated by 2 orders of magnitude compared to that bulk value. These findings illustrate how modest compositional changes reshape the interfacial environment to catalyze multiphase chemistry.