Using Salts to Explore and Control Gas-Liquid Interfacial Reactivity

Several recent studies show that the gas-liquid interface may provide a distinct reaction medium separate from the underlying bulk liquid. Our own molecular beam scattering studies indicate that DCl molecules impinging on liquid glycerol can undergo D to H exchange within the interfacial region and evaporate as HCl without penetrating into the interior of the liquid. Our current experiments demonstrate that we can control this interfacial exchange by dissolving alkali halide salts, such as KI, in glycerol. Direct comparisons of DCl to HCl exchange in salty and pure glycerol indicate that this interfacial reaction can be enhanced or suppressed depending on the concentration and identity of the ions in the liquid. By varying both the anion and cation of the salt, we can explore how ion size and charge density affect the composition, structure, and reactivity of the glycerol interface. These experiments will also assess the relative importance of ionic and nonionic pathways for the interfacial DCl to HCl exchange reaction.