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An Experimental and Theoretical Investigation of Atmospheric Hydrogen Bonded Systems in the Gas Phase /

  • Author(s): Louie, Matthew Kenneth
  • et al.
Abstract

The influence of hydrogen bonding in affecting the photochemistry and reactivity of several molecular systems that are atmospherically relevant has been investigated. Specifically, this thesis focuses on three different molecular systems in the gas phase including: the influence of intramolecular hydrogen bonding on the UV photochemistry of peroxyformic acid, the ability of formic acid to exploit intermolecular hydrogen bonding to catalyze the hydration of ketene, and the ability of water molecules to make use of intermolecular hydrogen bonding to catalyze the addition of amines to formaldehyde. For peroxyformic acid, we find that the presence of intramolecular hydrogen bonding results in a planar equilibrium structure in both its ground and first excited electronic states. This in turn affects the rotational energy imparted to the OH photofragments upon UV photodissociation. In the case of ketene hydration to form acetic acid, we have used ab-initio calculations to investigate the effectiveness of water versus formic acid in catalyzing the ketene hydration reaction. The energetics associated with two separate mechanisms was examined: one that led directly to acetic acid formation and another indirect path, which first forms an ene-diol intermediate. Lastly, the effect of water catalysis on the addition of a series of amines to formaldehyde in the gas phase was also studied using ab initio calculations. We compared the relative barrier heights for the addition of NH₃, methylamine and dimethylamine to formaldehyde. The barrier height decreased along the series and ultimately the water-catalyzed dimethylamine reaction was found to be barrierless in the gas phase

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