Tautomerization and Dissociation of Dimethyl Phosphonate Ions(CH3O)2P(H)=O•+:Theory and Experiment in Concert

The unimolecular gas phase chemistry of the title ion,(CH3O)2P(H)=O•+, (1•+) and its tautomer dimethyl phosphite, (CH3O)2P-OH•+, (2•+) was investigated using mass spectrometry based experiments in conjunction with computational quantum chemistry. A facile tautomerization of the "keto" ion 1•+ into its "enol" isomer 2•+ is prevented by a high 1,2-H shift barrier. Instead, 1•+ readily isomerizes via a 1,4-H shift to the very stable distonic ion …