EFFECTS OF FUNCTIONAL-GROUP INTERACTIONS ON THE BIOMOLECULAR AND DISSOCIATION REACTIONS OF DIOLS

The influence of functional group interactions on the bimolecular and dissociation reactions of diols were examined in a quadrupole ion trap mass spectrometer. Reactions of dimethyl ether ions with diols resulted in formation of (M + H)+ ions and (M + 13)+ ions (by net methyne addition). The product distribution depended on the relative separation of the hydroxyl groups within each diol, with the more proximate diols producing the greatest abundance of (M + 13)+ ions compared to (M + H)+ ions. The enhancement of the formation of (M + 13)+ ions is attributed to the capability for electrostatic interactions between the hydroxyl groups and the electropositive methylene group of the methoxymethylene reagent ion. The enhancement is most significant for diols that can adopt five- or to a lesser extent six-membered ring transition states (i.e., any 1,2 or 1,3 diol). Collision-activated dissociation (CAD) techniques, including both sequential activation experiments (MS(n)) and comparison of CAD spectra for model compounds, suggest that the (M + 13)+ ions are protonated cyclic diethers.