Investigations of structure and mechanism in organic reactions using kinetic isotope effects /
Heavy atom KIEs were obtained for the aliphatic Claisen rearrangement of allyl vinyl ether. These values were compared with those computed from theoretically determined transition structures and reactant structures. Attempts to describe the Claisen rearrangement in a two-dimensional format (More-O...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728908011&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Heavy atom KIEs were obtained for the aliphatic Claisen rearrangement of allyl vinyl ether. These values were compared with those computed from theoretically determined transition structures and reactant structures. Attempts to describe the Claisen rearrangement in a two-dimensional format (More-O'Ferral Jencks diagram) failed. It was concluded that the Claisen rearrangement bears a strong resemblance to the Cope rearrangement in terms of the mutability of its transition state, and the Claisen transition state may best be described as an interacting allyl and oxallyl fragment. Deuterium and ¹³C KIEs were used in conjunction with spectroscopic studies and theoretical calculations to determine the nature of a formyl C-H···X (X = F, Cl) interaction that appears to restrict the conformations of a number of chiral Lewis acid / aldehyde complexes that are important in enantioselective catalytic reactions. It was determined that the aldehydic proton is not participating in hydrogen bonding, and may be conformationally restricted by the anomeric effect. The radical cation-catalyzed Diels-Alder cycloaddition of 1,3-cyclohexadiene with indole was studied via ¹³C KIEs. A stepwise mechanism is consistent with the results. In light of previous studies, both experimental and theoretical, it appears that the formation of the first bond in the cycloaddition step itself is rate limiting. Intramolecular and intermolecular ¹³C KIEs were used to study the Friedel-Crafts acetylation of durene. In light of the KIEs obtained and relative rate studies, three conclusions can be reached: 1) The disparity between intramolecular and intermolecular KIEs obtained leads to the conclusion that the product-determining step is different from the rate-determining step. 2) The rate-determining step is the formation of a charge transfer []-complex involving durene. 3) The product-determining step is the formation of the []-complex. Finally, the diimide reduction of pentene was studied using both protiated diimide and d₂-diimide. The similarity of both predicted and measured secondary ²H and primary ¹³C KIEs for reduction with both labeled and unlabeled diimide leads to the conclusion that tunneling is either largely inoperative or is mediated by solvent motion. This conclusion is corroborated by the magnitude of the primary ²H KIEs obtained for the reduction of 9-decenol. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiii, 151 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 138-150). |