COLLISION-INDUCED RADICAL LOSSES FROM EVEN-ELECTRON NEGATIVE-IONS IN THE GAS-PHASE

Both radicals and (even-electron) neutrals are lost when even-electron organic negative ions are subjected to collisional activation in the gas phase. Generally, radical loss is less pronounced and less diagnostic (of some structural feature) than the ubiquitous (even-electron) neutral loss. There are exceptions to this generalisation: these often fall into one of the following classifications, i.e. ABCDRBAR --> ABCDBAR. + R., and ABCRBAR --> ABCBAR. + R. (R often = H or Me) There is a further type of "radical" loss, which is a stepwise process involving loss of H. and (R - H). This occurs in particular cases and only when R is alkyl (greater-than-or-equal-to Et). The reactions are diverse but they may all be rationalized as proceeding through five-membered ring intermediates. The loss of "C2H5" from an alkylcarboxylate anion is a suitable example: [GRAPHICS].