Evidence for Gas-Phase Hydrogen-Bonded Complexes of the Form [CH3+/CH3OH] and [CH3+/CH3OCH3]

Studies of unimolecular dissociation (MIKES) of ions formed in a chemical ionization ion source show that under CI conditions, the reaction of CH 3 + with CH 3 OH or CH 3 OCH 3 leads to the covalent structures (CH 3 ) 2 OH + or (CH 3 ) 3 O + . In contrast a FT-ICR study indicates that these reactions lead either to covalent structures by C−O bond formation and to [CH 3 + /CH 3 OH] or [CH 3 + /CH 3 OCH 3 ] ion−neutral complexes. Ab initio calculations confirm that such complexes correspond to minima on the potential energy surface. Their geometries correspond to a species in which a hydrogen of the CH 3 + cation is weakly bonded to the oxygen of the neutral. The interaction energies are ∼20 kcal/mol.