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

摘要

The effect of hydration on the reactivity of 0(-)(H20)n(n = 0-2) with theneutrals 02, C02, C0, N0, SO2, CH4, N20, AND H20 has been investigated as a function of temperature. Rate constants for the above reactions were measured at 251, 343, and 473 K (0(-)(H20)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 0(-) was found to decrease the reactivity for the neutrals C0, S02, CH4, and N20. For reactions of 0(-)(H20)n with 02, no reaction was observed for n = 0, but hydration of 0(-) enabled reaction to proceed for 0(-)(H20)1,2. For reaction with NO, addition of one H20 ligand to 0(-) increased the reactivity, while addition of a second H20 caused a decrease in the rate constant to a value below that of the unsolvated 0(-). No reaction was observed for any of the ions 0(-)(H20)0-2 with H20. Temperature dependences of the rate constants were found to vary depending on the system. Preliminary results from ab initio calculations yield an estimate of > or = kcal/mol for the 0(-)...H20 cluster bond strength. (TTL)