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Thesis - Open Access

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Master of Science (MS)




The first law of photochemistry, formulated in the works of Grotthus and Draper more than a century ago, states: Only the light which is absorbed by a molecule can be effective in producing photochemical change in the molecule. The law and its consequences are commonly taken for granted by photo chemists today. Until the advent of quantum mechanics, the effect of light on matter was not properly understood. As a result, during the primeval age of photochemistry numerous and wondrous photochemical reactions were discovered, but both useful application of these results and formulation of a unifying theory were lacking. From 1920 to 1950, photochemistry was perhaps considered the realm of the physical chemist who studied the details of photoreactions in the gas phase. The availability of new spectroscopic and analytical techniques during the l950's to the present date and the development of important theories concerning electronically excited states, reduced the difficulty in characterizing the complex products of photoreactions and gave promise of control of photochemistry. In the last decade the chemical literature was to a very large extent crowded with studies involving the controlled photochemistry of organic compounds, particularly those containing carbon and hydrogen only. More recently many studies have been extended to those compounds containing heteroatoms such as oxygen, nitrogen, and sulfur. The photochemistry of carbon pi bonded to oxygen in unconjugated ketones has been exhaustively studied. Similar studies on Azomethines (carbon pi bonded to a nitrogen) have also been reported. Although a certain amount of photochemistry has been done on compounds containing the conjugated thiones, there are no documented reports on the photochemistry of carbon pi bonded to sulfur in molecules containing this system as a simple unconjugated chromophore. This project was undertaken in an attempt to increase our knowledge of photochemical reactions about compounds containing the unconjugated thiocarbonyl chromophore. The main areas of interest and those studied include the reaction mechanisms and kinetic studies of the photochemistry of tetramethyl-3-thio-1,3- cyclobutanedione.

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South Dakota State University