Mechanistic aspects of high-energy collision-induced dissociation proximate to the charge in saturated fatty acid N-butyl esters cationized with lithium. Evidence for hydrogen radical removal

The high-energy collision-induced dissociation spectra of [M+Li](+) ions of n-butyl palmitate or heptadecanoate and their labelled isotopomers containing a H-2(2)-label at the C-2, C-3 and C-4 positions are reported, As is the case for positions remote from the charge, the removal of a hydrogen radical at proximate positions has been found to be an initial and decisive fragmentation reaction when [M + Li](+) ions are subjected to high-energy collision-induced dissociation, It is also demonstrated that direct C-C cleavage involving gamma bonds relative to the carbonyl bond or bonds more remote from the charge may be regarded as a secondary fragmentation route, Direct C-C cleavage of the beta bond should, however, be considered as a reaction competitive with C-H cleavage in the formation of the corresponding distonic ions. (C) 1997 John Wiley & Sons, Ltd