Gas-phase studies of distonic m-benzyne analogues in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer and the determination of the heats of formation for phenyl radicals in a flowing-afterglow guided ion beam (FA-GIB) mass spectrometer
Abstract
Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry provides an incredibly flexible and powerful method to study ion-molecule reactions that would be difficult to study otherwise. For example, the FT-ICR technique allows the investigation of reactive intermediates that are difficult to study in condensed phase. A class of reactive intermediates that are of great interest due to the antitumor properties of some members are the benzynes and their analogues. The goal of this work was to expand the body of knowledge pertaining to m-benzynes and their analogues. The reactivity of a negatively charged m-benzyne analogue, 3,5-didehydrobenzoate, was found to be controlled by its polarity, resulting in this m-benzyne reacting as a nucleophile. A systematic examination into the factors that control the reactivity of m-benzynes in general revealed that the reactivity of a m-benzyne can be "tuned" to favor either nonradical addition/elimination reactions or radical-type reactions simply by changing the constitution or position of substituents. The hydroxyl group was found to induce radical-type reactivity in m-benzyne analogues, but only when it is adjacent to one (but not both) of the two dehydrocarbon atoms. A study of a novel σ,σ,π-triradical revealed that the σ,σ-biradical moiety is substantially more reactive than the π-radical moiety, which contributes to reactivity after reactions have quenched the σ-radical sites. Finally, a thermochemical investigation of charged aromatic monoradicals combines computations, proton affinity bracketing, and energy-resolved collision-induced dissociation, to deduce the heats of formation for these species.
Degree
Ph.D.
Advisors
Kenttamaa, Purdue University.
Subject Area
Analytical chemistry
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