Protonated ethanol and its neutral counterparts.

Collisionally activated dissociation and neutralization-reionization experiments reveal that protonation of ethanol leads to two distinct isomers, the classical ion CH3CH2OH+2 and the proton-bound complex C2H4… H+… OH2. The neutral counterpart of the latter is unstable, whereas that of the former can be produced in a bound state if the CH3CH2OH+2 precursor ion is formed under low ion source pressure conditions and, thus, with higher internal energies. This suggests that there are substantial differences in the geometries of CH3CH2OH(+) 2 and the hypervalent CH3CH2OH2·. This provides only a partial explanation for unusual isotope effects; C2H5OD2·, CH3CD2OD2·, and CD3CH2OD2. are substantially more stable than C2D5OD2 · and C2H5OH2·.