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INVESTIGATION OF THE PYROLYSIS OF LIGNIN BY USING COLLISION-INDUCED DISSOCIATION CHARGE-REMOTE FRAGMENTATION MASS SPECTROMETRY
thesisposted on 30.04.2021, 00:30 by Cory J Conder
Mass spectrometry of negative ions is a convenient method for generating, isolating, and analyzing reactive intermediates that would otherwise be too short lived to detect. This ion approach is especially useful for studying the chemical properties of radicals. In this work, a negative charge-carrying group was attached to lignin model compounds and combined with collision-induced dissociation (CID) to generate and characterize radical species involved in the primary pyrolysis of lignin. The charge-tag served to increase the sensitivity of the model compounds using electrospray ionization mass spectrometry (ESI-MS) and promoted charge-remote fragmentations (CRF) upon being collisionally activated. The resulting product ions were comparable to the primary pyrolysis products of lignin; thus, CID-CRF proved to be an effective way of identifying the mechanisms by which lignin decomposes in the gas phase.
Additionally, this dissertation includes a review of nitrene anions. Nitrene anions are another class of reactive intermediates protected by an electron that provide a means for studying the corresponding neutral molecules via electron photodetachment spectroscopy and photoelectron spectroscopy. The added electron makes it possible for protected nitrene anions to be manipulated by external electric and magnetic fields of a mass spectrometer. Nitrene anions also display their own unique reactivities as reagents, which have been investigated using ion/molecule reactions. Mass spectrometry of negative ions has thereby provided information on the electronic states, reactivities, and thermochemical properties of nitrene intermediates.