MONTE CARLO COMPUTER SIMULATION STUDIES OF DIMETHYLPHOSPHATE ANION.
Item
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Title
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MONTE CARLO COMPUTER SIMULATION STUDIES OF DIMETHYLPHOSPHATE ANION.
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Identifier
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AAI8708294
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identifier
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8708294
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Creator
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JAYARAM, BHYRAVABHOTLA.
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Contributor
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David L. Beveridge
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical
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Abstract
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This dissertation is a collection of theoretical calculations on diverse aspects of the dimethylphosphate anion (DMP('-)) in aqueous solutions and in free space based on Monte Carlo computer simulation methods. In addition, some extensions of the formal theory of environmental effects based on the dielectric continuum model were carried out. The individual topics considered are as follows.;Aqueous hydration of DMP('-), and Na('+)DMP('-) ion pair, with the two phosphodiester torsion angles in the gauche-gauche (gg), gauche-trans (gt) and trans-trans (tt) conformations were investigated using liquid state Monte Carlo computer simulation method in (T,V,N) ensemble at 25(DEGREES)C. The structural and energetic aspects of the hydration of each molecule were analyzed using the proximity criterion and were partitioned into ionic, hydrophilic and hydrophobic contributions. Free energy simulations were performed on DMP('-) (,aq) in the gg, gt and tt conformations using the probability ratio method. The performance of the simulations on the thermodynamic cycle was also examined.;The intramolecular thermodynamics of the gg, gt and tt conformations of DMP('-) in free space were determined by the Monte Carlo method, with configurational entropies estimated in the quasiharmonic approximation. Both inter and intramolecular thermodynamics favored the gg conformation of DMP('-) relative to gt and tt forms.;The solvation shell model, modified by incorporating the coordination numbers and first sheel radii obtained from the mean energy simulations was used to independently evaluate the relative free energies of hydration of the gg, gt and tt conformations of DMP('-) and to provide a comparison with the results of Monte Carlo free energy studies.;In related studies from another point of view, the Tanford-Kirkwood theory for evaluating the electrostatic free energy of a discrete charge distribution in the presence of ion atmosphere was extended to concentric dielectric continua, and applied to study the conformational preferences of DMP('-) and Na('+)DMP('-) in the absence and presence of ion atmosphere and at varying local dielectric constants. Theoretical extensions of coaxial cylindrical dielectric continua to evaluate environmental free energies were also carried out.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Chemistry
