The negative ion mass spectra of deprotonated carbohydrates. Part 1. The basic hydroxymethyl-substituted ring systems

Tetrahydrofuran-2-methanol and tetrahydropyran-2-methanol are models for the basic ring systems of simple carbohydrates. These compounds deprotonate, in the gas phase, principally at the HO group. The major fragmentations of these systems involve competitive losses of H2O and CH2O. Labelling (18O and 2H), and product ion studies, indicate that proton transfer between the 3-position on the ring and –CH2O– yields a 3-anion which immediately ring opens. The ring opened alkoxide may undergo proton transfers which effectively make both of the oxygens equivalent. Other tetrahydrofuran- and tetrahydropyran-methanols also undergo ring cleavage: their negative ion spectra show subtle differences.