Gas-phase fragmentation reactions of protonated cocaine: New details to an old story.

Abstract

AbstractWe have used a combination of multiple stage mass spectrometry (MSn) experiments, hydrogen/deuterium exchange experiments, and thermochemical data estimated by computational chemistry calculations at the B3LYP/6‐31+G(d,p) level of theory to revisit the gas‐phase fragmentation of protonated cocaine. The lone pair of nitrogen participates in major fragmentation routes of protonated cocaine, to generate cyclic iminium ions. The structure of product ion m/z 182, which has been previously proposed in the literature, was shown to be unstable; therefore, we have decided to revisit it. Here, we propose another ion structures for the product ion m/z 182 that is supported by thermochemical data. Compared with the formation of other product ions, the formation of the most intense product ions in the collision‐induced dissociation spectrum of protonated cocaine (m/z 182 and m/z 82) is the most energetically favorable. We propose the structure and formation of m/z 122 and m/z 91 for the first time. We suggest that m/z 91 originates from m/z 122 instead of m/z 119, as fully supported by MSn experiments. The results of this study could help to study and quantify cocaine metabolites.