Ion-Neutral Complex Intermediate for Loss of Water from Fatty Acid Carboxylates

Article abstract of DOI:10.1002/oms.1210270412

Fatty acid carboxylates desorbed into the gas phase by fast atom bombardment (FAB) undergo both metastable-ion and collisionally activated dissociation (CAD) to eliminate water.Upon CAD, the water elimination competes with charge-remote fragmentation.Deuterium labeling results are in accord with the elimination occurring via an ion-neutral complex involving hydroxide ion and neutral ketene.Evidence that the precursor of the ion-neutral complex is the enol form of the carboxylate was obtained by forming the enolate directly by decarboxylation of appropriate dicarboxylic acids.The <(M-H-CO2>(1-) ions of these species undergo a more facile elimination of water than do carboxylates desorbed directly upon FAB.