Effects of Hydration on Reactions of O- (H2O)n (n = 0-2). 1. Temperature Dependences of Rate Constants for Reactions with O2, CO2, CO, NO, SO2, CH4, N2O, and H2O

Article abstract of DOI:10.1021/j100384a039

The effect of hydration on the reactivity of O^- (H2O)n (n = 0-2) with the neutrals O2, CO2, CO, NO, SO2, CH4, N2O, and H2O has been investigated as a function of temeprature.Rate constants for the above reactions were measured at 251, 343, and 473 K (O^-(H2O)2 reactions were studied at 251 and 343 K only) by using a variable-temperature fast-flow system that incorporates optionally either a selected ion source or a high-pressure ion source.Hydration of O^- was found to decrease the reactivity for the neutrals CO, SO2, CH4, and N2O.For reactions of O^-(H2O)n with O2 and CO2, no reaction was observed for n=0, but hydration of O^- enabled reaction to proceed for O^-(H2O)1,2.For reaction with NO, addition of one H2O ligand to O^- increased the reactivity, while addition of a second H2O caused a decrease in the rate constant to a value below that of the unsolvated O^-.No reaction was observed for any of the ions O^-(H2O)0-2 with H2O.Temperature dependences of the rate constants were found to vary depending on the system.Preliminary results from ab initio calculations yield an estimate of >/=25 kcal/mol for the O^---H2O cluster bond strength.