Gas-phase ion chemistry of the pesticide imidacloprid: Proton driven radical fragmentation of the nitro-guanidine functional group

Abstract

Electrospray ionization (ESI) coupled with low-energy collision-induced dissociation (CID) was used to establish the role of the charge in the fragmentation reactions of the [M+H] +, [M+CH 3] + (a methylated fixed charge derivative), [M-H] - and [M+Li] + of imidacloprid, 1, which contains both a nitroguanidine functional group, a known 'explosophore', and a remote chloropyridine group. The major primary fragmentation pathways involve fragmentation of the nitroguanidine functional group in all cases, although the type of neutrals lost varies. Bond homolysis via NO 2 loss is a major fragmentation pathway for [M+H] + (∼55% relative abundance), but is virtually absent for [M+CH 3] + (in which th..