Thesis - Open Access
Master of Science (MS)
William S. Wadsworth
Organophosphorus compounds are one of the most important classes of chemical compounds found in plant and animal systems. Organophosphorus compounds are also important industrial chemicals used in building materials and in pesticides. Two typical organophosphorus pesticides are diazionan and malathion. In biological systems organophosphorus compounds are active constituents found in cell membranes and they are important mediators of energy transfer and storage processes. Energy liberated during biochemical processes is stored in the form of an organophosphate, adenosine triphosphate(ATP). The stored energy can be made available to the cell for its biochemical reactions that require energy input. During the course of glucose degredation, 3-phosphoglyceraldehyde is oxidized to 3-phosphoglycerate and the energy of oxidation is stored in the form of ATP. However the mechanism by which the energy is transferred is not indicated by the above overall reaction. The reaction takes place in two steps which involve the phosphorylated derivative of the acid,ie 3-phosphoglycerate, 1. The phosphorylated derivative of 3-phosphoglycerate, 1, is a mixed anhydride of phosphoric and carboxylic acids, an acetyl phosphate. The compound is unusual for a number of reasons. a) It has a standard free energy of hydrolysis substantially greater than that of adenosine triphosphate. b) It is a common intermediate in the above two sequential biochemical reactions. It is the· product of the first reaction and the reactant of the second reaction. As seen 3-phosphoglyceraldeyde is n6t oxidized directly to 3phosphoglycerate but to a mixed anhydride, an acetyl phosphate. Therefore acetyl phosphates (mixed anhydrides of phosphoric an& carboxylic acids) are important mediators in energy transfer and storage processes. Because of their importance and the unique properties of ' these compounds, it is important to learn more about their chemistry. It has been theorized that the hydrolysis of acetyl phosphates takes place by a dissociative mechanism, involving a common intermediate, a metaphosphate, Figure 5. 0 Conclusions surrounding the dissociative mechanism, though widely accepted can neither be substantiated nor fully denied. The existence of a metaphosphate intermediate is skeptical and is currently a matter of debate. Reactions where evidence strongly supports it's existence are carried out under conditions and with structural modification which are far removed from those found under physiological conditions. The goal of our research is to find satisfactory answers concerning the chemical properties of acetyl phosphates. We used our own model system of aroyl phosphates and with this system studied their isomerization and nucleophilic reactions. We also studied the effect of metal catalyst on the methanolysis of the model systems. In order to observe if a dissociative mechanism is operational we studied the chemistry of a mixed anhydride of methane trifluoro sulfonic and phosphoric acid, a compound which contains an excellent leaving group.
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South Dakota State University
Ahmed, Abdihakim O., "Aroyl Phosphates : Evidence for the High Reactivity of Acyl Phosphates" (1988). Electronic Theses and Dissertations. 4751.