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 47 for “"bond breaking"”.
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Development of a ReaxFF force field for glyphosate and investigation of its abiotic degradation pathways
… degrades in the environment via C-P and C-N bond dissociation. Depending on the specific reaction pathway, toxic or non-toxic metabolites may form, however, the factors that influence the selection or predominance of a given degradation pathway are not entirely understood. The ReaxFF force …
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Binary molecular diffusivities in liquids: prediction and comparison with experimental data
… use of regular solution theory by relating the bond breaking energy of the jump step to the bond breaking energy in evaporation. Diffusivities estimated by this equation and the equations developed by Olander, by Gainer and Metzner, and by Wilke and Chang were compared with experimental data. …
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Multi-Configurational Investigation of Thermolytic Pathways of Highly Strained Ring Systems
… the potential energy surfaces (PES's) for ? bond breaking and ? bond rotation in these highly strained structures. Of particular interest was how would resonance and or electronegativity affect the allowed/disallonature of the activation barriers in these systems. The two model systems of …
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Shape Selective Oxidations of Hydrocarbons
… consistent with a greater amount of C-H bond breaking in the iron transition state. Shape selectivity was used as a sensitive probe for metalloporphyrin involvement in the hydroxylation transition state. Both tert-butylhydroperoxide and trifluoroethanol solubilized …
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Proton-coupled electron transfer : from basic principles to small molecule activation
… Despite the importance of PCET in such catalytic bond-making and bond-breaking reactions, the underlying mechanisms by which electron and proton transport couple to one another are not particularly not well understood. To address mechanistic issues surrounding the role of PCET in long range charge …
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Theoretical studies of thermal syn elimination reactions
… It was determined that the C$\sb\alpha$-O bond appears to be breaking first in the reaction. It was also found that the effect of polar substituents agree with experimental results. Electron withdrawing groups in the $\beta$ position were found to change the order of bond breaking to …
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Investigations of the Electric Field Dependencies of the Generation Rates of Oxide and Interface Traps on Silicon
… threshold is consistent with the hydrogen bond-breaking model which indicates a threshold kinetic energy of 3-4 eV for trap generation by energetic electron impact. From the subthreshold slope and fractional transconductance change of the I$\sb{\rm D}$-V$\sb{\rm G}$ characteristics stressed …
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A stereoelectronic and thermodynamic study of b-D-methyl glucose conformational changes related to anomeric centre reactivity
… nucleophile. What is the effect of the C1-O1 bond breaking process on key glucose properties is the central question asked and answered in this thesis. A battery of ab initio methods is used to uncover details of the glucose ring pucker free energy volumes. The free energy volumes were …
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Dowel-concrete contact characteristics
… the effect of dowel bar diameter and type of bond-breaking agent on the friction coefficient and the magnitude of dowel-pulling force. The results indicate that the use of silicone as bond-breaker produces lower dowel-concrete coefficient of friction than that obtained using Tectyl (506). The …
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Small-molecule activation chemistry catalyzed by proton-coupled electron transfer
… Despite the importance of PCET in such catalytic bond-making and bond-breaking reactions, the underlying mechanisms of coupled proton and electron transport in these processes is not well understood. To address mechanistic issues surrounding the role of PCET in catalytic chemical transformations, …
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Spectroscopic investigations of the X and A state dynamics of ¹³C₂H₂
… state. Acetylene exemplifies one of the simplest bond-breaking isomerization systems and it has served as a prototype for studies of large amplitude vibrational motion in molecules. The short-time, large amplitude, vibrational dynamics of acetylene are well understood up to the acetylene - …
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Studies in Selective C-C Bond Formation via Borylation and Dehydrogenation
Three stories of C-C bond formation are presented. First, we attempt to harness the Lewis acidity of boron to induce chemo- and regioselectivity in two fundamental organic reactions (Chapter 1). We explore 1,2-difunctionalization of alkenes via formation of a three-membered cyclic intermediate with …
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Three dimensional vibrational spectroscopy and shock initiation of hmx
… mechanisms of initiation for HMX. Those first bond breaking events are poorly understood, and much could be learned from experimental observation. Much refinement of the sample design was done, but there was still no events observed by SFG that were clearly attributable to HMX initiation. No …
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Atomistic characterization of stress-driven configurational instability and its activation mechanisms
… sharp crack tips, and chemically-enhanced bond breaking in a wet silica nanorod. These processes are studied in a unified manner such that two important types of properties are determined: one is the athermal load at which the instability takes place instantaneously without the aid of …
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Interactions of platinum compounds with heterocyclic bases.
… energetics of dissociation of platinum-nitrogen bonding have been investigated, using simple model bases, namely pyridine. pyrimidine. purine and some derivatives. Six complexes of the type cis-PtCl2L2, where L is a N-heterocycle, have been successfully prepared and characterized. The kinetics of …
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Molecular manipulation with the scanning tunnelling microscope
… and requires 1.4 \(\pm\) 0.1 electrons per C-Cl bond breaking event. Based on work and previous work, we suggest this is a mixture of a two-electron temperature independent and one-electron temperature dependent processes. The activation barrier for the thermally assisted one-electron …
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A Computational Investigation of the Mechanism of CB1954 Reduction by E.coli Nitroreductase
… and electron transfer concerted with N-O bond breaking, regardless of the source (FMN or solution) or order of the protons. Molecular mechanics calculations with the FF03 force field found a binding mode with the amide group of CB1954 bound in the active site of NTR—an orientation ideally …
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Atomic -Scale Statistical Models of Semiconductor Device *Reliability
… isotope effect of silicon-hydrogen (deuterium) bond dissociation by electronic excitation for both the interface and scanning tunneling microscope induced silicon-hydrogen bond-breaking on the silicon surface. We demonstrate the distribution of silicon-hydrogen bond energies as the physical …
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Shock compression and flash-heating of molecular adsorbates on the picosecond time scale
… to probe the shock initiation or first bond-breaking reactions in molecular explosives such as δ-HMX: a necessary study for the development of safer and more effective energetic materials.
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