Reactions of anionic water clusters X^-(H₂O)_n, n = 1-50, X = OH and O, with hydrochloric acid

Reactions of anionic water clusters of the type X^-(H₂O)_n, (n = 1-50, X = OH and O) with hydrochloric acid have been investigated under single-collision conditions in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. For all the clusters studied, the first step consists in replacement of the anionic X^- core with a chloride anion. A series of subsequent ligand exchange and fragmentation reactions result in terminal anions of the types Cl^-(HCl)_n and Cl₂^-(HCl)_n in different proportions. The detailed reaction sequence is discussed, and formation of free OH radicals in the reactions of O^-(H₂O)_n anions is detected. To gain some qualitative insight into the anion geometry and structure, a series of ab initio calculations by a density functional approach was performed for selected clusters.