CHEMISTRY OF LARGE HYDRATED ANION CLUSTERS X-(H2O)N, N = 0-59 AND X = OH, O, O2, AND O3 .2. REACTION OF CH3CN

The kinetics and mechanisms of the gas-phase reactions of acetonitrile with large hydrated anion clusters X-(H2O)n=0-59, X = OH, O, O2, and O3, were studied in a fast flow reactor under thermal conditions. OH-(H2O)n=0-1 react with CH3CN at near collision rate via proton-transfer and ligand-switching mechanisms; further hydration greatly reduces the reactivity of OH-(H2O)n>1 due to the thermodynamic instability of the products compared to the reactants. On the contrary, for all cluster sizes studied, O-(H2O)n reacts with CH3CN at near the collision rate via a hydrogen transfer from acetonitrile to the anion clusters. A new reaction channel was found for the reaction of O- with CH3CN to form CHCN-, which can react further-with CH3CN to form CH2CN and CH2CN-. Only very slow associations were observed for the reactions of O2-and O3- and their hydrates. The possible application of the present experimental results to an understanding of the hydrolysis mechanism of CH3CN in aqueous solution in the presence of OH- and protons as a catalyst is also discussed.