The water-solvated methanol ion and its isomers: experiment and theory

Abstract

Tandem mass spectrometry combined with ab initio calculations was used to explore the chemistry of the water-solvated methanol cation and its isomers, including the distonic methanol ion solvated by water, CH 2OH 2 +/H 2O ( I), the methanol molecular ion associated with water, CH 3OH +/H 2O ( II), and protonated methanol bound with a hydroxyl radical, CH 3OH 2 +/HO ( IV). Another ion, [H 2O⋯HCH 2OH +] ( III), where the water molecule is attached to a methyl H of the methanol cation, proved inaccessible experimentally although it was predicted to be stable in a shallow potential well by theoretical calculations. The ions were generated by collision-induced loss of a radical or atom from appropriate proton bound molecular pairs. The heats of formation of ions ( I) to ( IV) were calculated to be 448, 482, 486 and 538 kJ/mol, respectively. Ions ( I), ( II) and ( IV) can be identified by their metastable ion and collision-induced dissociation mass spectra. A partial potential energy surface linking the isomers is used to discuss the experimental data obtained with deuterium-labeled species.