Measurements of equilibria and reactivity of cluster ions at atmospheric pressure: reactions of Cl-(CHCl3)0-2 with methyl bromide and methyl iodide

Measurements by the kinetic ion mobility mass spectrometer (KIMMS) of (i) equilibrium constants for the clustering reactions X-(CHCl3)i-1 + CHCl3 half arrow right over half arrow left X-(CHCl3)i, where X- = Cl- and Br- and i = 1 or 2, (ii) single ion mobilities for the ions Cl-(CHCl3)0-2 and Br-(CHCl3)0-1, and (iii) rate constants for the S(N)2 nucleophilic displacement reactions of a distribution of chloride cluster ions, Cl-(CHCl3)0-2, with CH3Br and with CH3I in nitrogen buffer gas at atmospheric pressure are reported. A unique feature of the present equilibrium and kinetic measurements is that they are obtained from ion mobility measurements and, therefore, are not subject to potential sources of error that can accompany mass spectrometric-based measurements involving aperture sampling of a high-pressure ion source. Another unique feature of the present investigation is that the reactivity of a selected set of cluster ions is determined under physical conditions in which the individual ions are kinetically labile with respect to cluster decomposition and growth.