• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • 1
  • Tagged with
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ortho substitution effects on the acidic and alkaline hydrolyses of formanilides

Desai, Salil Dileep 01 December 2009 (has links)
The objectives of this project were to determine the reaction schemes of formanilide and substituted formanilides in acidic and alkaline solutions, to quantiate the kinetics of hydrolysis, to propose reaction mechanisms, and to assess the role of ortho words substitution in formanilide hydrolysis kinetics. A set of thirty substituted formanilides were synthesized and characterized. Hydrolysis of the formanilides was carried out under first order conditions in hydrochloric acid (0.01-8 M, 40°C) and in hydroxide solutions (0.01-3 M, 25°C and 40°C). Hydrolysis kinetics were evaluated in terms of temperature (20°C- 60°C), solvent composition (0-50 % dimethyl sulfoxide, dioxane, ethanol and acetone) and ionic strength (0.1-1) effects. The degradation products were separated and identified using RP-HPLC, and the alkaline and acidic reaction schemes were proposed. For acidic hydrolysis of formanilides, the observed rate constants were proportional to the hydronium concentrations. Modified Hammett plots constructed using the second order rate constants for specific acid catalysis were linear. The ortho effect was analyzed using the Fujita-Nishioka method. In alkaline solutions the observed rate constants showed mixed first and second order dependences with respect to hydroxide concentration. A complex degradation scheme was used to estimate individual rate constants and to construct Hammett plots. Ortho effects were examined for the first order hydroxide concentration dependent pathway. Arrhenius plots for substituted formanilides were linear in both acidic and alkaline media. Ionic strength did not show any effect on the acidic and alkaline hydrolysis rates. In both acidic and alkaline media the rate of hydrolysis decreased with increase in organic solvent content. Formanilide hydrolyzes in acidic solutions by specific acid catalysis and the kinetic study results were consistent with AAC2 mechanism. Ortho substitution led to reduction in rates. The orthoeffect could be split in steric inhibition of resonance, retardation due to steric bulk and through space interactions. In alkaline solutions a complicated kinetic scheme was used to describe the multiple pathways of degradation. The results from the kinetic studies could be explained using a modified BAC2 mechanism. The hydrolysis of meta and parasubstituted formanilides in alkaline conditions did not show substituent effects however ortho substitution led to an decrease in rate constants proportional to the steric bulk of the substituent.
2

The Synthesis of Novel and Sterically Demanding Tetra-ortho-substituted Aryl Naphthalenes

Glass, Adam Cameron, 1983- 09 1900 (has links)
xiv, 326 p. : ill. (some col.) / Tetra-ortho -substituted aryl naphthalenes (TOANs) are a motif of great importance, being present in biologically active natural products, chiral ligands, and building blocks relevant to materials science. The synthesis of sterically demanding and enantioenriched TOANs continues to be a challenge for current synthetic methods. Herein, we describe the highly effective synthesis of a variety of sterically demanding and enantioenriched TOANs through a rearrangement-based method. Our method utilizes a cyclopropyl carbinol moiety as the key rearrangement precursor. We have demonstrated that carbon-carbon coupling through a simple nucleophilic attack on a cyclopropyl indanone allows for very large aryl substrates to be added and rearranged. We discuss in detail the following: 1) the initial substrate-scope and proof-of-concept studies, 2) our progress in building the most sterically demanding TOANs to date, and 3) the asymmetric synthesis of TOANs through chiral transfer. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Michael M. Haley, Chairperson; Shih-Yuan Liu, Advisor; Darren W. Johnson, Member; Victoria J. DeRose, Member; Paul J. Wallace, Outside Member

Page generated in 0.0829 seconds