Author (Your Name)

Ta-Chung Ong, Colby College

Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Chemistry Dept.


D. Whitney King

Second Advisor

Thomas W. Shattuck


The highly reactive nature of superoxide anion presents an analytical challenge to prepare stable standards for instrument calibration. McDowell et al. (1983) developed a convenient method of superoxide production based on continuous photolysis of benzophenone and acetone in oxygen saturated, alkaline, 2-propanol solution. In the McDowell reaction, ketones are photolyzed to their triplet state, and then reacted with alcohol to produce ketyl radicals that react with oxygen to produce superoxide. This study investigated the mechanism and rate of these reactions by Laser Flash Photolysis (LFP). Reaction rate constants for the reaction between the benzophenone triplet and ethanol was 5.5 x 105 M-1s-1, and between the benzophenone ketyl radical and oxygen was 1.8 x 109 M-1s-1, consistent with published literature values. The reaction rates and mechanism were incorporated into a STELLA-based kinetic model to predict superoxide production and decay on a time scale of minutes. The model provided optimal conditions for superoxide production in terms of pH and alcohol concentration. The model predictions of superoxide production agree with experimental photolysis results. The model shows that the optimal condition of superoxide production is at 12 M alcohol concentration (ethanol) at pH 13. The actual photolysis results show that the optimal alcohol concentration is 6-9 M at pH 13.


Superoxide, Synthesis Photochemistry, Laser photochemistry, Reaction mechanisms, Flash photolysis

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