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Title of Thesis

Fahim Uddin
Institute/University/Department Details
University of Karachi/ Department of Chemistry
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
thionine, n-penyl-glycine, n-allylurea, n-phenylurea, thiourea, thionine

The photochemical reduction of thionine by N-Penyl-glycine, N-allylurea, N-phenylurea and thiourea in absolute methanol was investigated. An apparatus for the irradiation of air free solutions, with known intensities of monochromatic lights was constructed. Double walled glass reaction cell was devised in which nitrogen inlet/outlet, water inlet/outlet arrangements were made. Acidities of the reaction solutions were controlled using buffer solutions. Acidities determined spec-trophotometrically using basic indicator were expressed in terms of a Hamett acidity function. Variations of quantum efficiencies in absolute methanol have been determined at various concentrations of thionine, reductants, and acidities. The oxygen free reaction solutions were irradiated and the reactions were followed by measuring the intensity of light transmitted.

The quantum efficiency, in yellow light, for the dis-appearance of thionine, was found to be a function of reductant concentration, acidity and temperature. The quantum efficiency was found to be independent of the concentration of thionine. The results have been interpreted in terms of a reaction mechanism. Ratios of the certain rate constants for the proposed mechanism have been evaluated. It was found that the quantum efficiency is controlled by two equilibriums between: i) triplet state of thionine with protion, and protonated triplet state of thionine, and ii) protonated triplet state of thionine with reductant, and associated complex of thionine with reductant.

Download Full Thesis
1034.25 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 2 Literature Survey 4
348.91 KB
  2.1 Introduction 4
  2.2 Protonated Forms of Thionine 4
  2.3 The Processes Representing the Photochemical Reduction of Dyes 11
  2.4 Reactions with Organic Reductants 12
  2.5 Reactions with Inorganic Reductants 26
  2.6 Photooxidation 40
  2.7 Electron Transfer Processes and Reactivity of Triplet State of Thionine 41
  2.8 Photosensitized Reactions of Thionine 42
  2.9 Effect of Inhibitors on the Photochemical Reactions of Thionine 43
  2.10 Fluorescence of Thionine Dye 44
  2.11 Photolysis of Thionine 49
  2.12 Aim of the Present Work 53
2 3 Experimental 54
170.46 KB
  3.1 Introduction 54
  3.2 Apparatus 56
  3.3 Measurement of Light Intensity 64
  3.4 Measurement of the Acidity of the Reaction Solution 67
  3.5 Materials 70
  3.6 Preparation of Stock Solutions 74
  3.7 Procedure 77
3 4 Results 79
331.42 KB
  4.1 Determination of Quantum Efficiency 79
  4.2 Order of Presentation of Experimental Data 89
  4.3 Reactions of Thionine with N-Phenlglycine in Absolute Methanol 89
  4.4 Reactions of Thionine with N-Allylurea in absolute Methanol 95
  4.5 Reactions of Thionine with N-Phenylurea in Absolute Methanol 102
  4.6 Reactions of Thionine with Thiourea in Absolute Methanol 107
4 5 Discussion 131
326.05 KB
  5.1 Introduction 131
  5.2 Reactions with N-Phenylglycine in Absolute Methanol 132
  5.3 Reactions with N-Allylurea in Absolute Methanol 133
  5.4 Reactions with N-Phenylurea in Absolute Methanol 134
  5.5 Reactions with Thiourea in Absolute Methanol 135
  5.6 General Mechanism of the Reaction 136
  5.7 Determination of the Ratios of the Rate Constants of Thionine Reductant Reactions 151
  5.8 Conclusion 162
  5.9 Comparison with Earlier Work 163
  5.10 Recommendations and Future Work 167
  5.11 References 169
  5.12 Appendix 1 179