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| Title: | Study on the reaction kinetics of the chemical oxidation of o-phenylenediamine with ammonium persulfate |
| Authors: | Hohenstein, Edward G. |
| Issue Date: | 21-Jan-2008 |
| Abstract: | 2,3-Diaminophenazine (DAP) has been extensively studied at Washington College.9-12 The origins of the interest in DAP lie in an enzyme kinetics experiment used in the General Chemistry Laboratory. In this experiment, DAP is formed due to the oxidation of o-phenylenediamine (OPD) catalyzed by horseradish-peroxidase with hydrogen peroxide. The Journal of Chemical Education article,8 on which this experiment is based, suggests that the kinetics of this reaction can be followed by either a colorimeter or a spectrophotometer. In practice, the results gathered by these two instruments are strikingly different. The origins of these differences have been investigated for several years. This study looks at the oxidation of OPD with a chemical oxidant, ammonium persulfate. Most of the experiments in this study were based on a Journal of Organic Chemistry article.13 This study replicated the synthesis of 3-aminophenazin-2-ol (APO), a second product, along with DAP, of the oxidation of OPD with ammonium persulfate in 1 M HCl, described in this article. The kinetics of this oxidation were followed spectrophotometrically for a variety of conditions. Also, the claim made by Iseminger et al.13 that DAP is hydrolyzed to APO in 1 M HCl was tested. It was determined that the mechanism proposed by Iseminger et al.13 was incorrect. Based on a mechanism for the enzyme catalyzed oxidation of OPD by Xie, Li, et al.2 this study proposes a mechanism for the chemical oxidation of OPD with ammonium persulfate. The Runge-Kutta-Fehlberg method was used to approximate solutions to the system of differential equations describing the mechanism proposed by this study and the mechanism proposed by Iseminger et al.13 Numerical data were fit to the experimental data by varying the rate constants for the steps in the mechanisms. The analysis of the mechanism proposed by
Iseminger et al.13 showed that it could not correctly describe the behavior of the oxidation of OPD. The mechanism proposed by this study could, using well chosen rate constants, describe the experimental behavior of this reaction. A unique set of rate constants was not found that could be used to fit the calculated data to all the experimental data, but a set of rate constants could be found which would fit the calculated data to a single kinetics run. |
| Description: | Submitted in partial fulfillment of the requirements
for the degree of Bachelor of Science. Department of Chemistry
Department of Mathematics and Computer Science. May 2007 Thesis Adviser: James R. Locker, Ph.D., Eugene Hamilton, Ph.D. |
| URI: | http://hdl.handle.net/10090/3792 |
| Appears in Collections: | Washington College Mathematics Senior Capstone Experience
Washington College Chemistry Senior Capstone Experience
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| Hohenstein_CHE&MAT.pdf | | 1316Kb | Adobe PDF | View/Open |
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