RADICAL PROCESSES IN REMOTE CHARGE FRAGMENTATIONS OF LITHIUM-CATIONIZED LONG-CHAIN ALKENYL AND ALKADIENYL SALICYLIC ACIDS

Multistep radical processes are proposed to rationalize the formation of product ions formed by collisionally induced and spontaneous fragme ntation of lithium-cationized 6-alkenyl and 6-alkadienyl salicylic aci ds. An important step in these processes consists of a homolytic C-H c leavage, a mechanism which is consistent with the charge-remote concep t. Evidence is given by the observation that the fragmentation of ions formed by the loss of a hydrogen radical is similar to that found for the precursor [M-H+2Li](+) ions. The proposed mechanisms also explain very well the observed enhanced abundances of ions whose formation in volves formal benzylic, homobenzylic and homoallylic cleavages. The en hanced abundance of ions whose formation involves formal allylic cleav ages can be readily rationalized by resonance stabilization of interme diate allylic radical ions.