KINETICS AND MECHANISM STUDIES OF SWITCHING AND ASSOCIATION REACTIONS INVOLVING NA+-LIGAND COMPLEXES

The kinetics and mechanisms of the reactions of Na+· (X)n = 0_3, X = water, ammonia, and methanol with CH 3CN, CH3COCH3, CH3CHO, CH 3COOH, CH3COOCH3, NH3, CH 3OH, and CH3-O-C2H4-O-CH 3(DMOE) were studied at ambient temperature under different pressures. All of the switching (substitution) reactions proceed at near-collision rate and show little dependence on the flow tube pressure, the nature and size of the ligand, or the type of core ions. Interestingly, all of the measured rate constants agree well with predictions based on the parametrized trajectory calculations of Su and Chesnavich [J. Chem. Phys. 76, 5183 (1982)]. The reactions of the bare sodium ion with all neutrals proceed via a three-body association mechanism and the measured rate constants cover a large range from a slow association reaction with NH3, to a near-collision rate with DMOE. The lifetimes and the dissociation rate constants of the intermediate complexes deduced using the parametrized trajectory results, combined with the experimentally determined rates, compare fairly well with predictions based on RRKM theory. The calculations also account for the large isotope effect observed for the clustering of ND3 and NH3 to Na+. © 1990 American Institute of Physics.