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dc.contributor.advisorSingleton, Daniel A.en_US
dc.creatorNowlan, Daniel Thomasen_US
dc.date.accessioned2005-08-29T14:38:21Z
dc.date.available2005-08-29T14:38:21Z
dc.date.created2003-05en_US
dc.date.issued2005-08-29
dc.identifier.urihttp://hdl.handle.net/1969.1/2308
dc.description.abstractTransition metal catalyzed reactions have an important place in synthetic chemistry, but the mechanistic details for many of these reactions remain undetermined. Through a combination of experimentally determined 13C kinetic isotope effects (KIEs) and density functional theory (DFT) calculations, some of these reactions have been investigated. The cyclopropanation of an olefin catalyzed by rhodium (II) tetrabridged complexes has been shown to proceed through an asynchronous, but concerted mechanism. DFT does not provide an accurate transition structure for the reaction of an unstabilized carbenoid with an olefin, but it does predict an early, enthalpically barrierless transition state which is consistent with the reactivity of unstabilized carbenoids. For the case of stabilized carbenoids, the theoretical structures predict the KIEs accurately and a new model is proposed to explain the selectivity observed in Rh2(S-DOSP)4-catalyzed cyclopropanations. The chain-elongation step of atom transfer radical polymerization (ATRP) has been shown to be indistinguishable from that of free radical polymerization (FRP) for the CuBr/2,2??-bipyridine system. While DFT calculations predict an earlier transition state than observed, the calculations suggest that with increasing levels of theory the predicted KIEs come closer to the observed KIEs. A recently proposed [2 + 2] mechanism for the cyclopropenation of alkynes catalyzed by Rh2(OAc)(DPTI)3 has been shown not to be a viable pathway. Rather, the experimental KIEs are predicted well by canonical variational transition state theory employing the conventional mechanism for cyclopropenation via a tetrabridged rhodium carbenoid. DFT calculations also suggest an alternative explanation for the observed enantioselectivity. The 13C KIEs for metal-catalyzed aziridination have been measured for three separate catalytic systems. While the KIEs do not completely define the mechanism, all of the reactions exhibit similar KIEs, implying similar mechanisms. A surprising feature of this system is the presumed nitrene intermediate??s triplet spin state. This complicates the DFT analysis of this system.en_US
dc.format.extent1200252 bytes
dc.format.mediumelectronicen_US
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen_US
dc.publisherTexas A&M Universityen_US
dc.subjectMechanismen_US
dc.subjectkinetic isotope effectsen_US
dc.subjectcatalysisen_US
dc.subjectcyclopropanationen_US
dc.subjectcyclopropenationen_US
dc.titleMechanisms of transition-metal catalyzed additions to olefinsen_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.committeeMemberAnthony, Rayford G.en_US
dc.contributor.committeeMemberBergbreiter, David E.en_US
dc.contributor.committeeMemberBurgess, Kevinen_US
dc.type.genreElectronic Dissertationen_US
dc.type.materialtexten_US
dc.format.digitalOriginborn digitalen_US


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