Gas-phase equilibria studies of C 2H 2N + and C 3H 4N + with CH 3CN

Abstract

Thermodynamic quantities, ΔH° n−1, n and ΔS° n−1, n , for the gas-phase clustering reactions of C 2H 2N + and C 3H 4N + with CH 3CN have been studied using a pulsed electron beam high-pressure mass spectrometer. For the C 2H 2N +(CH 3CN) n clusters studied, in the first step the C 2H 2N + ion was seen to disappear rapidly after the electron pulse and the equilibrium of this ion for the reaction forming C 2H 2N + ·CH 3CN was not observed under conditions of the experiments. In the case of C 3H 4N +(CH 3CN) n , the − ΔH° n−1, n values show a large gap with n = 1 → 2, suggesting that the adduct ion, C 3H 4N + ·CH 3CN, is a core in the cluster. Comparison of the bond enthalpies of C 2H 2N +(CH 3CN) n ⩽ 5 and C 3H 4N +(CH 3CN) n ⩽ 4 with those of alkali metal ions solvated by CH 3CN shows that at n ⩾ 2 the ion-ligand interaction in the clusters is mainly electrostatic.