Negative ion fast atom bombardment and collision-induced dissociation mass spectrometry of the 2-, 3-, 4- and 6-deoxy derivatives from methyl beta-D-galactopyranoside and related compounds.

The fast atom bombardment collision-induced dissociation mass spectra of the [M-H]- ions of the 2-, 3-, 4- and 6-deoxy derivatives from methyl beta-D-galactopyranoside and some related compounds have been recorded. The fragmentation reactions of these quasimolecular ions and of OD-labelled analogues have been examined and related to the molecular structure. In some cases distinct and common mechanisms can be derived, but it is also clear from these experiments that not only the site of deprotonation of the molecules, but also the anticipated charge localization in the fragment ions strongly direct the fragmentation reactions.