A Stereochemical Approach toward the Structure of Gas-Phase Ions

The stereoselectivities for hydrogen abstraction in the electron impact induced loss of acetic acid from three 1,2-disubstituted ethyl acetates as well as the loss of water from three acyclic secondary alcohols have been determined. This information was sought in an attempt to (1) help define the general limits for conformational analysis in the study of gas-phase ions and (2) determine the structural relationships, fundamental to conformation, among the various gas-phase ions and accessible phase molecules studied. In each case, i.e., elimination of acetic acid and loss of water, the results are stereochemically comparable to the analogous thermal reactions, i.e., formation of olefins from the pyrolysis of the subject acetates and 1,4-hydrogen abstraction by the alkoxy radicals derived from the alcohols studied. The overall results may be seen as a stereochemical extension of the historical structure-reactivity approach to ion structure in inaccessible gas-phase molecular radical cations. The success of these stereochemical experiments, along with the results of others in related studies, clearly recommends this type of approach to the elucidation of the nonbonded features of gas-phase ion structure unavailable by present methodology.