rdf-syntax-grammar
mods:
  schema location: http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
  title info:
    title: Mechanistic Investigation of Rearrangement of Ammonium Ylides
  name:
    name part: Biswas, Bibaswan
    role:
      role term: creator
    role:
      role term: author.
  name:
    name part: Singleton, Daniel Allen
    role:
      role term: thesis advisor.
  name:
    name part: Texas A & M University
    role:
      role term: degree granting institution.
  type of resource: text
  genre: bibliography
  origin info:
    place:
      place term: txu
    date issued: 2015
    issuance: monographic
  language:
    language term: eng
  physical description:
    form: remote
    extent: 1 online resource.
  abstract: A central aim of physical organic chemistry is the elucidation of reaction mechanisms. This knowledge is then usable in the rational control of reactions and the development of new synthetic methodology. A reaction mechanism is generally viewed as consisting of the sequence of intermediates and transition states connecting starting material and products, and it would be expected that any experimental observation can be understood from the mechanism. In this way, the applicability of transition state theory (TST) is an implicit assumption in the description of reaction mechanisms and particularly the understanding of rates and selectivity. However, TST sometimes fails to account for experimental outcomes. The main goal of this dissertation is to investigate mechanisms of reactions where ideas outside of TST are needed to explain observations. The origin of competing [2,3]- and [1,2]-rearrangements of ammonium-ylides was studied. The [2,3]-rearrangement is an allowed concerted pericyclic reaction while the [1,2]-rearrangement is forbidden and should occur by a stepwise process. The mechanism was investigated by a combination of experiments, standard theoretical calculations and dynamic trajectory calculations. The experiments include the measurement of kinetic isotope effects (KIEs), crossover experiments and temperature dependence of product ratio. The theoretical calculations predict an early and loose transition state for [2,3]-rearrangements. The theoretically predicted KIEs are in good agreement with experimental KIEs. Dynamic trajectories from an early and loose [2,3]-transition state showed that from a single transition state there is a bifurcation on the free energy surface. One of the paths is concerted that leads to [2,3]-rearrangment product. However, an alternative path involving cleavage leads to diradicals that can recombine to give both [1,2]- and [2,3]-products. This partitioning of dynamic trajectories was supported by the crossover experiment because…
  note: by Bibaswan Biswas.
  note: "Major Subject: Chemistry"
  note: Includes vita.
  note: Doctor of Philosophy Texas A & M University 2015 http://hdl.handle.net/1969.1/155561
  note: Includes bibliographical references.
  note: Text (Dissertation)
  subject:
    topic: Major chemistry
  subject:
    topic: Sigmatropic rearrangement
  subject:
    topic: Sommelet-Hauser
  subject:
    topic: Stevens
  identifier: http://hdl.handle.net/1969.1/155561
  record info:
    record content source: TXA
    record creation date: 160927
    record change date: 20170926145526.0
    record identifier: in00003735255
    language of cataloging:
      language term: eng