Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 79 for “"transition states"”.
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Transition states in the evolution of the mammalian sex chromosomes
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 1998.
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Stabilization of transition states of organic reactions by cyclodextrins, micelles, and dendrimers
… linear correlation between the substrate and the transition state binding for different acetals and orthoesters, which reflects the importance of both nature of the substituent, and its location in the molecule of the substrate. Amino- and carboxylate-terminated dendrimers modestly catalyze the …
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Enzyme-Catalyzed Phosphoryl Transfer Reactions: Energetics of Transition States and Vanadate Analogues in Aqueous Solution
… solution to address the use of Vanadium(V)-based transition state analogues in the study of DNA Polymerase, β-phosphoglucomutase (β-PGM), and Hexose Phosphate Phosphatase (HPP) -catalyzed phosphoryl transfer reactions. This work seeks to add to the growing body of theoretical work that addresses …
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I. Catalyst development in asymmetric phase transfer catalysis employing QSAR methods II. Computational investigations on the stereochemical course of the addition of allylsilanes to aldehydes
… with experimental model systems, the synclinal transition states are determined to be preferred over the antiperiplanar transition states in the electrophilic-activated manifolds and vice versa for the fluoride-activated manifold. The selectivity for the syn diastereomer in the electrophilic …
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Computational modeling of organic structure, spectra, and reactivity
… that cannot be examined experimentally, such as transition states. These transition states can lend themselves to better understanding of the system's reactivity. Modeling can also be used to perform analysis that would time-consuming and tedious experimentally or clarify ambiguous experimental …
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Olefin oligomerization reactions theoretical studies using cyclometallated palladium(II) catalysts and experimental studies on platinum(II) analogues
… energies were calculated for intermediates and transition states for both Cossee-type and metallacycle mechanisms.
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Asymmetric Catalysis with Brønsted Acids: Experiments and Calculations
… used in order to find diastereomeric transition states and to understand how the catalyst induces chirality during the enantiodetermining step. Furthermore, through these DFT calculations, an alternative mode of activation for the imine substrate was envisaged, different from the usual …
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Density Functional Theory: Development and Applications
… to both the treatment of barrier heights and transition states (Chapter 7) and then proceed to make it continuous and capable of treating an entire reaction coordinate (Chapter 8).
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Aspects of structural and electronic disorder in network materials: approaches to simulation
… Linear Maximization) for prediction of transition states by simulation, and its application to diffusion simulations in both crystalline network silicates and silica glass.
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DFT Studies of the Organocatalytic Aldol Reaction and a Frustrated Lewis Pair
… thesis describes methods to consider different transition states of the proline- catalyzed α-chlorination aldol reaction to determine the reasonable transition state in the reaction between the enamine and α-chloro aldehydes. Moreover, the novel intramolecular Frustrated Lewis pair based on a …
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Investigating the role of information technology in resolving governance challenges in a transition state - the case of Tanzania
… and practitioners and more so for the transition economies which are characterised by weak institutions, insecurity, political instability and poor IT skills and capabilities. Limited studies have been conducted to examine this problem in transition states in Africa. The objective of …
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Studies in Asymmetric Catalysis: Lewis Base Catalyzed, Enantioselective Addition of Trimethylsilyl Cyanide, Trimethylsilyltrifluoromethane, and Glycolate-Derived Silyl Ketene Acetals to Aldehydes
… be rationalized by the analysis of six open transition states with the aid of computational calculation.
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Mirroring Enzymes: The Role of H-Bonding In HQuin-BAM Catalyzed Asymmetric Aza-Henry Reactions: A DFT Study into the Reactivity, Mechanism, and Origins of Selectivity
… of the stereodetermining C-C bond forming transition states for monoalkylated nitronate addition to a range of electronically different aldimines, revealed that the origins of stereoselectivity were controlled by a delicate balance of different factors such as steric, orbital interactions, …
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The Application of Catalysis based on Hydrogen Bonding and Ion-pairing Interactions to Asymmetric Minisci-type Alkylations of Azines and Iridium-Catalysed C-H Borylation.
… with Dr Kristaps Ermanis on the nature of the transition states for oxidative addition of symmetrical benzhydrylamides and phosphinamides. Density functional theory (DFT) calculations by Dr Ermanis suggested contrasting conformations for the oxidative addition of the two substrate classes and …
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Thermochemistry and kinetic analysis on radicals of acetaldehyde + O2, allyl radical + O2 and diethyl and chlorodiethyl sulfides
… for reactants, intermediates, products and transition states important in the radicals of acetaldehyde + O_2 and allyl radical + O_2 reaction systems are analyzed with density functional and ab initic calculations, to evaluate the reaction paths and kinetics in oxidation and pyrolysis. …
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Computational Evaluation of Mechanistic Pathways of Action of Superoxide Dismutase
… Activation energies were computed for various transition states complex involved in concerted, two step and three step mechanisms catalyzed by [Cu(NH<sub>3</sub>)<sub>4</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. Based on this analysis, mechanisms which include the peroxy radical …
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Development of transition state analogues targeting chitinases and oligosaccharyl transferase
… pathways, they are believed to share similar transition states involving an oxocarbenium ion. To understand the mechanism of OT and discover potent and selective inhibitors against different chitinases, our intent was to utilize the common transition state analogue for both enzymes and …
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Computational Analysis of Molecules and Chemical Reactions from Cheminformatic Databases
A large number of organic reactions feature post-transition state bifurcations. Selectivities in such reactions are difficult to analyse because they cannot be determined by comparing the energies of competing transition states. Molecular dynamics approaches can provide answers but are …
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Part 1: Progress Toward the Total Synthesis of Platensimycin. Part 2: Aromatic Ions: Carbon-Based Nucleofuges and Chiral Cyclopropenones and Formamides
… also studied for their use in chlorodehydration. Transition states for enantiodifferentiation are proposed.
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Measurement of the rate of hydrogen atom abstraction from methane and ethane by muonium
… of the title reactions, in location of the transition states on the potential energy surfaces. Also, for the Mu variants, the reaction rates seem to be reduced less for vibrationally excited states of CH₄ and C₂H₆than for the ground states than is the case for the corresponding H atom …
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