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Theoretical Studies of Reactive Intermediates in Complex Reaction Mechanisms

Coldren, William Henry
http://orcid.org/0000-0003-2260-3809
http://rave.ohiolink.edu/etdc/view?acc_num=osu1531497707269833

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Chemistry.
The mechanistic transformations of three fundamental classes of reactive intermediates are explored: singlet and triplet carbenes, carbene radical cations, and carbon-centered radicals. Through a marriage of theory and ultrafast spectroscopy, the identities of unique carbene species and photochemical transformations were characterized from nitrogenous (diazo and diazirine) precursors. The photochemistry of a novel trifluoro-diazo, carbenic precursor (ethyl 2-diazo-3,3,3-trifluoropropanoate) is explored by ultrafast time-resolved infrared spectroscopy in multiple solvents and the results do not reveal a prototypical 1,2-migration product via rearrangement in the excited state or through a carbene intermediate. The primary photochemical process is the interconversion of a diazo functional group to the corresponding diazirine. A completely new mechanistic pathway is detailed for the conversion of diazo and diazirine containing nitrogenous precursors to their corresponding products. This theoretical report accounts for the partially unexplained and curious bifurcation in photochemical vs thermal decomposition of nitrogenous precursors. Using a phenanthrene precursor, the first ultrafast time-resolved spectroscopic observation of a vinyl carbene (singlet ¿-methylbenzylidenecarbene) is reported and the results are supported and rationalized by computational data. Electronic factors affecting the regioselectivity of aryl radical hydrogen-atom abstraction reactions in benzyl-alkyl tethered species is explored in order to guide efforts of selective remote C–H functionalizations. The system can be biased towards or away from the standard abstraction pathway by the use of electron-donating and electron-withdrawing groups strategically placed on the benzene ring. The mechanistic aspects of the oxidative transformation of C2 symmetric o-aminophenol species and C3 symmetric formyl fragments to form benzobisxazole based covalent organic frameworks (COFs). Computational data strongly suggest that such reactions occur via a putative radical species that is stabilized by an active captodative effect. The nature of the catalysts used affects the efficiency of this reaction and the overall crystallinity and porosity of desired COFs. Preliminary investigations into the difficulty of resurrecting aged huAChE based on the nature of organophosphorus chemical nerve agents are presented. The active site is severely contracted for a methyl phosphonate aged enzyme compared to an alkyl phosphate aged enzyme. In silico prediction of factors influencing the binding and activity of novel quinone methide precursors as potential therapeutics is investigated with biophysical molecular dynamics simulations and in the case of one substrate, the efficacious enantiomer was predicted a priori to experimental in vitro screening.
Christopher Hadad, PhD (Advisor)
Jon Parquette, PhD (Committee Member)
David Nagib, PhD (Committee Member)
Karl Werbovetz, PhD (Committee Member)
271 p.
Chemistry
Reactive Intermediates; Computational Chemistry; Organophosphorus Nerve Agent Chemistry; Carbenes; Radicals; Molecular Dynamics

Recommended Citations

Citations

  • Coldren, W. H. (2018). Theoretical Studies of Reactive Intermediates in Complex Reaction Mechanisms [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531497707269833

    APA Style (7th edition)

  • Coldren, William. Theoretical Studies of Reactive Intermediates in Complex Reaction Mechanisms. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1531497707269833.

    MLA Style (8th edition)

  • Coldren, William. "Theoretical Studies of Reactive Intermediates in Complex Reaction Mechanisms." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531497707269833

    Chicago Manual of Style (17th edition)

osu1531497707269833
535
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This open access ETD is published by The Ohio State University and OhioLINK.