Methylene substitution reactions in a quadrupole ion trap selectivity of ethylene, ethylene oxide, and dimethyl ether reactive ions.

To elucidate the selectivity of methylene substitution reactions of monosubstituted and disubstituted oxyaromatic compounds in a low pressure quadrupole ion trap environment, the relative abundances of covalently bound and loosely bound adducts formed by ion/molecule reactions with ethylene (ET), ethylene oxide (ETOX), and dimethyl ether (DME) were compared. Adduct ions of all three reagent gases were formed in both a conventional ion source and a quadrupole ion trap and characterized by collisionally activated dissociation. For DME and ET, the covalently bound adducts formed at (M + 45)(+) and (M + 41)(+), respectively, are direct precursors to the methylene substitution product ions at (M + 13)(+). ETOX and ET do not demonstrate the same functional group selectivity for methylene substitution as previously observed for DME. This is attributed to differences in reaction exothermicities and competing reactions.