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dc.contributor.advisorBühl, Michael
dc.contributor.authorCrawford, Luke
dc.coverage.spatial345en_US
dc.date.accessioned2015-11-19T09:54:04Z
dc.date.available2015-11-19T09:54:04Z
dc.date.issued2015-11-30
dc.identifier.urihttp://hdl.handle.net/10023/7818
dc.description.abstractCatalysis is a key area of chemistry. Through catalysis it is possible to achieve better synthetic routes, exploit molecules normally considered to be inactive and also attain novel chemical transformations. The development of new catalysts is crucial to furthering chemistry as a field. Computational chemistry, arising from applying the equations of quantum and classical mechanics to solving chemical problems, offers an essential route to investigating the underlying atomistic detail of catalysis. In this thesis calculations have been applied towards studying a number of different catalytic processes. The processing of renewable chemical sources via homogeneous reactions, specifically cardanol from cashew nuts, is discussed. All routes examined for monoreduction of a diene model by [Ru(H)(iPrOH)(Cl)(C₆H₆)] and [Ru(H)(iPrOH)(C₆H₆)]⁺ are energetically costly and would allow for total reduction of the diene if they were operating. While this accounts for the need of high temperatures, further work is required to elucidate the true mechanism of this small but surprisingly complex system. Gold-mediated protodecarboxylation was examined in tandem with experiment to find the subtle steric and electronic effects that dictate CO₂ extrusion from gold N-heterocyclic carbene activated benzene-derived carboxylic acids. The origin of a switch in the rate limiting step from decarboxylation to protodeauration with less activated substrates was also clearly demonstrated. Studies of gold systems are closed with examinations of 1,2-difluorobenzene C–H activation and CO₂ insertion by [Au(IPr)(OH)]. Calculations highlight that the proposed mechanism for oxazole-derived substrates cannot be extended to 1,2-difluorobenzene and instead a digold complex offers more congruent predicted kinetics. The lens of quantum chemistry was turned upon palladium-mediated methoxycarbonylation reactions. An extensive study was undertaken to attempt to understand the bidentate diphosphine ligand dependency on forming either methylpropanoate (MePro) or copolymers. Mechanisms currently suggested in literature are shown to be incongruous with the formation of MePro by Pd(OAc)₂ and bulky diphosphines. A possible alternative route is proposed in this thesis. Four mechanisms for methoxycarbonylation with Pd(2-PyPPh₂)ₙ are detailed. The most accessible route is found to be congruent with experimental reports of selectivity, acid dependency and slight steric modifications. A modification of 2-PyPPh₂ to 2-(4-NMe₂-6-Me)PyPPh₂ is shown to improve both selectivity and turnover, the latter by four orders of magnitude (highest transition state from 22.9 kcal/mol to 16.7 kcal/mol ∆G), and this new second generation in silico designed ligand is studied for its applicability to wider substrate scope and different solvents. The final chapter of this thesis is a mixed quantum mechanics and molecular mechanics (QM/MM) examination of an enzymatic reaction, discussing the need for certain conditions and the role of particular amino acid residues in an S[sub]N2 hydrolysis reaction.en_US
dc.language.isoenen_US
dc.publisherUniversity of St Andrews
dc.rightsCreative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subjectChemistryen_US
dc.subjectCatalysisen_US
dc.subjectHomogeneous catalysisen_US
dc.subjectEnzymesen_US
dc.subjectEnzymatic catalysisen_US
dc.subjectDensity functional theoryen_US
dc.subjectDFTen_US
dc.subjectComputational chemistryen_US
dc.subjectAlkoxycarbonylationen_US
dc.subjectC-H Activationen_US
dc.subjectProtodeaurationen_US
dc.subjectProtonolysisen_US
dc.subjectMethanolysisen_US
dc.subjectPalladiumen_US
dc.subjectRutheniumen_US
dc.subjectGolden_US
dc.subjectQM/MMen_US
dc.subjectThermodynamicsen_US
dc.subjectKineticsen_US
dc.subjectTransition statesen_US
dc.subjectPhosphinesen_US
dc.subject.lccQD505.C8
dc.subject.lcshCatalysisen_US
dc.subject.lcshQuantum chemistryen_US
dc.subject.lcshHomogeneous catalysisen_US
dc.subject.lcshTransition metal catalystsen_US
dc.subject.lcshEnzymes--Biotechnologyen_US
dc.titleMechanistic insights into enzymatic and homogeneous transition metal catalysis from quantum-chemical calculationsen_US
dc.typeThesisen_US
dc.type.qualificationlevelDoctoralen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US
dc.rights.embargodate2019-10-23
dc.rights.embargoreasonThesis restricted in accordance with University regulations. Print and electronic copy restricted until 23rd October 2019, pending formal approvalen_US


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