Evidence for Interfacial [FDCl]− in Collisions between DCl and F− in KF−Glycerol Solutions

• Published in: Journal of physical chemistry. C 2008-10, Vol.112 (39), p.15449-15457
• Main Authors: DeZwaan, Jennifer L, Brastad, Susan M, Nathanson, Gilbert M
• Format: Article
• Language: English
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp805224p

Fluoride ions dissolved in glycerol readily react with DCl molecules from the gas phase when they come into contact in the near-interfacial region. These reactions are investigated by directing DCl molecules at the surface of 0.5−4.0 M KF−glycerol solutions in vacuum and monitoring the velocities and residence times of the DCl, HCl, and HF products. Although F− ions are expected to be repelled from the surface region, we find that they radically alter two near-interfacial channels: the submicrosecond conversion of DCl into HCl and desorption of intact DCl. F− ions eliminate rapid DCl → HCl exchange at concentrations of 2.5 and 4.0 M KF, instead converting DCl into HF molecules that slowly desorb from solution. F− ions also steal away thermalized DCl molecules that would have desorbed from the surface of pure glycerol. This scavenging of DCl by F− implies that some F− ions approach DCl molecules near the surface and form [FDCl]−. The complex then decays into DF and Cl−, followed by DF → HF exchange and slow HF evaporation. Among the halide ions investigated, only F− suppresses near interfacial DCl → HCl exchange and DCl desorption whereas I− and Br− enhance these processes. The F− ion, however, appears to be more effective than I−: in a mixture of 1.6 M KI and 1.6 M KF, I− ions only slightly inhibit scavenging of DCl by F−.