Mass Spectrometric Study of Ion-Solvent Molecule Interactions in the Gas Phase

Important and hitherto unavailable information on ion-solvent molecule interactions can be obtained from the mass spectrometric detection of ion clusters in the gas phase. Individual solvation step enthalpies and entropies for the reactions A + · (n — 1)S + S = A + · nS can be obtained. The systems where A + = NH 4 +, H 3 O +, Na + and S = NH 3 and H 2 O are described. The comparative solvation of Cl -, BCl -, and B 2 Cl - by water is described. In a study of the competitive solvation of CH 3 OH 2 + by water and methanol, it is found that methanol is more strongly solvating at close range of the ion. At larger distances (large clusters) water is taken up preferentially. The ammonium ion shows a distinct inner shell of four solvent molecules. Ammonia is taken up preferentially into this shell while water is taken up preferentially into the outer shell.