Interfacial Interactions of DCl with Salty Glycerol Solutions of KI, NaI, LiI, and NaBr

• Published in: Journal of physical chemistry. C 2007-10, Vol.111 (41), p.15043-15052
• Main Authors: Muenter, Annabel H., DeZwaan, Jennifer L., Nathanson, Gilbert M.
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp074616n

Gas−liquid scattering experiments are used to explore the role of interfacial ions in controlling collisions and reactions of DCl molecules with ∼2.5 M KI, NaI, LiI, and NaBr glycerol solutions. DCl molecules that thermalize upon collision with the surface of each solution follow one of three pathways:  they may desorb immediately as DCl, undergo D → H exchange in the near-interfacial region and desorb as HCl, or dissolve and dissociate in the bulk. We find that each salt amplifies the differences among the channels:  the fraction of DCl molecules that desorb intact increases from 9% for pure glycerol to 18% on average for the salt solutions, interfacial DCl → HCl exchange increases from 3 to 7%, and bulk dissolution drops from 87 to 75%. Dissolved ions may enhance nonreactive DCl desorption and interfacial D → H exchange by tying up glycerol OH groups, which will impede both DCl−OH bonding and migration of D+ and H+ away from Cl- after DCl ionization. Despite differences in the sizes of the ions and their interactions with the solvent, the enhancements are found to be similar for NaI, LiI, and NaBr and slightly smaller for KI. These similarities may arise from an interplay between ion pairing, the strength and number of ion−solvent bonds, and ion exposure at the surface.