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dc.contributor.advisorSingleton, Daniel A.en_US
dc.creatorWang, Zhihongen_US
dc.date.accessioned2007-04-25T20:11:37Z
dc.date.available2007-04-25T20:11:37Z
dc.date.created2005-12en_US
dc.date.issued2007-04-25
dc.identifier.urihttp://hdl.handle.net/1969.1/4886
dc.description.abstractSeveral organic reactions that could potentially involve coarctate transition states were investigated by a combination of experimental and theoretical studies. In the thermal fragmentation of ∆-1,3,4-oxadiazolines, the mechanism supported by kinetic isotope effects and theoretical calculations is a three-step process that does not demonstrate any special stabilization in coarctate transition states. Rather than undergoing a direct coarctate conversion to product, the mechanism avoids coarctate steps. The last step is a concerted coarctate reaction, but being concerted may be viewed as being enforced by the necessity to avoid high-energy intermediates. In the deoxygenation of epoxides with dichlorocarbene, the stabilization from the transition state aromaticity is not great enough to compete with the preference for asynchronous bonding changes. KIEs and calculations suggested that the reaction occurs in a concerted manner but with a highly asynchronous early transition state with much more Cα-O bond breaking than Cβ-O bond breaking. In the Shi epoxidation, a large β-olefinic 13C isotope effect and small α-carbon isotope effect indicated an asynchronous transition state with more advanced formation of the C-O bond to the β-olefinic carbon. The calculated lowest-energy transition structures are generally those in which the differential formation of the incipient C-O bonds, the "asynchronicity," resembles that of an unhindered model, and the imposition of greater or less asynchronicity leads to higher barriers. In reactions of cis-disubstituted and terminal alkenes using Shi's oxazolidinone catalyst, the asynchronicity of the epoxidation transition state leads to increased steric interaction with the oxazolidinone when a π-conjugating substituent is distal to the oxazolidinone but decreased steric interaction when the π-conjugating substituent is proximal to the oxazolidinone. Dynamic effects were studied in Diels-Alder reaction between acrolein and methyl vinyl ketone. This reaction yields two products in a ratio of 3.0 ± 0.5. Theoretical studies shows that only one transition structure is involved in the formation of both. Quasiclassical trajectory calculations on an MP2 surface give a prediction of a product ratio of 45:14 (3.2:1), which is in good agreement with the experimental observation.en_US
dc.format.extent1132278 bytes
dc.format.mediumelectronicen_US
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen_US
dc.publisherTexas A&M Universityen_US
dc.subjectkinetic isotope effectsen_US
dc.subjectdynamic effectsen_US
dc.subjectmechsnistic studiesen_US
dc.titleKinetic isotope effects, dynamic effects, and mechanistic studies of organic reactionsen_US
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentChemistryen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorTexas A&M Universityen_US
thesis.degree.nameDoctor of Philosophyen_US
thesis.degree.levelDoctoralen_US
dc.contributor.committeeMemberBergbreiter, David E.en_US
dc.contributor.committeeMemberBurgess, Kevinen_US
dc.contributor.committeeMemberTsai, Jerryen_US
dc.type.genreElectronic Dissertationen_US
dc.type.materialtexten_US
dc.format.digitalOriginborn digitalen_US


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