Theoretical studies of chemical processes in solution
Abstract
Statistical perturbation theory and Monte Carlo simulations have been utilized to obtain interionic potentials of mean force for the separation of tert-butyl chloride and tetramethylammonium chloride ion pairs in dilute aqueous solution at 25$\sp\circ$ and 1 atm. For both species, the solvent mediated free energy profiles revealed the existence of contact and solvent-separated ion pairs. In both cases, the solvent-separated minimum is broad and is not energetically distinct from free ions. The features in the tert-butyl chloride free energy profile are stronger including a larger barrier between the contact and solvent-separated ion pairs due to the greater orientation preferences the tert-butyl cation has for coordination to the counterion or a water molecule. Statistical perturbation theory has also been applied to a study of the conformational equilibria of aqueous (n-butane and n-pentane. The free energy profiles for dihedral angle rotation in water indicate that for these aldanes, the more compact conformers are favored in aqueous solution relative to the gas phase. Finally, thermodynamic cycle perturbation theory has been used with Monte Carlo simulations to efficiently calculate the absolute binding free energy for a methane dimer in water. The calculation gave results with good precision, in agreement with other theoretical studies and should serve as a prototype for similar calculations on larger systems.
Degree
Ph.D.
Advisors
Jorgensen, Purdue University.
Subject Area
Chemistry
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