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Hydroxyl Radical Additions to Arenes a Dissertation

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Hydroxyl Radical Additions to Arenes a Dissertation HYDROXYL RADICAL ADDITIONS TO ARENES A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE DOCTOR OF PHILOSOPHY BY LEE COURTLAND MOORES DR. JAMES S. POOLE - ADVISOR BALL STATE UNIVERSITY MUNCIE, INDIANA JULY 2015 HYDROXYL RADICAL ADDITIONS TO ARENES A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE DOCTOR OF PHILOSOPHY BY LEE COURTLAND MOORES DISSERTATION ADIVISOR: DR. JAMES S. POOLE APPROVED BY: _________________________________________ ________________ Committee Chairperson Date _________________________________________ ________________ Committee Member Date _________________________________________ ________________ Committee Member Date _________________________________________ ________________ Committee Member Date _________________________________________ ________________ Committee Member Date _________________________________________ ________________ Dean of Graduate School Date BALL STATE UNIVERSITY MUNCIE, INDIANA JULY 2015 ABSTRACT DISSERTATION: Hydroxyl Radical Addition to Arenes STUDENT: Lee Courtland Moores DEGREE: Doctor of Philosophy COLLEGE: Sciences and Humanities DATE: July 2015 PAGES: 201 Anthropogenic input of organic compounds into aqueous environments and the effects of these contaminants on ecosystems, as well as human health are of great concern. Many contaminants are found in concentrations in excess of the accepted daily intake (ADI) values. The fate of these contaminants as they degrade by chemical processes, specifically via reactions with hydroxyl radicals (·OH), and the rate of that degradation, is of interest. Hydroxyl radicals are a major contributor to the breakdown of many contaminants in natural systems. The present study focused on measuring the product distributions from the reactions of selected substrates with ·OH, and the determination of rates of reactions relative to benzene (PhH). From the data collected, models for predicting degradation pathways and rates of larger, more complex molecules can be developed. In this study ·OH was generated by thermolysis, and reacted with two competing substrates. The products of the reaction were trapped with TEMPO, a nitroxyl radical, then derivatized to allow for analysis and characterization by GC/MS. The ratios of ·OH addition products yield relative rate coefficients that may be subjected to Arrhenius analysis to probe the effect of structure on reactivity. TABLE OF CONTENTS CHAPTER 1 - INTRODUCTION ................................................................................................. 1 1.1 Organic Pollutants: Some Representative Classes ......................................................... 2 1.1.1 Polycyclic Aromatic Hydrocarbons (PAHs) ........................................................................ 3 1.1.2 Polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs) ............... 4 1.1.3 Agrochemicals .................................................................................................................. 6 1.1.4 Pharmaceuticals and Illicit Drugs ...................................................................................... 7 1.1.5 Structural Features of Contaminants ................................................................................10 1.2 Sources, Transport, Fates and Treatment of Environmental Contaminants .................13 1.2.1 Sources, Transport and Fates of Contaminants ...............................................................13 1.2.2 Treatment of Contaminants in Wastewater .......................................................................15 1.3 Hydroxyl Radical Chemistry .............................................................................................18 1.3.1 Natural Sources of Hydroxyl Radicals ..............................................................................19 1.3.2 Reactions of Hydroxyl Radicals with Organic Compounds ...............................................21 1.3.3 Measuring Hydroxyl Radical Reactivity and Selectivity in Solution ...................................31 1.4 A Method for the Study of Hydroxyl Radical Chemistry .................................................34 CHAPTER 2 – EXPERIMENTAL METHODOLOGY ................................................................. 41 2.1 Materials and Instrumentation .........................................................................................41 2.2 Experimental Methods ......................................................................................................48 2.2.1 Kinetic Studies in Benzene ...............................................................................................48 2.2.2 Degradation of Peroxide Initiator in Acetonitrile ................................................................50 i 2.2.3 Kinetic Studies in Acetonitrile ...........................................................................................51 2.2.4 Gas Chromatography Mass Spectrometry (GC/MS) .........................................................52 CHAPTER 3 – THE REACTIVITY AND SELECTIVITY OF HYDROXYL RADICAL REACTIONS IN HYDROCARBON SOLVENTS .......................................................................57 3.1 Introductory Remarks .......................................................................................................57 3.2 Selectivity of Hydroxyl Radical Addition to Toluene (Methylbenzene) .........................59 3.3 Selectivity of Hydroxyl Radical Addition to other Aromatic Substrates .......................65 3.3.1 o-Xylene (1,2-Dimethylbenzene) ......................................................................................65 3.3.2 m-Xylene (1,3-Dimethylbenzene) .....................................................................................67 3.3.3 p-Xylene (1,4-Dimethylbenzene) ......................................................................................70 3.3.4 Anisole (Methoxybenzene) ...............................................................................................70 3.3.5 Trifluorotoluene (α,α,α-Trifluoromethylbenzene) ...............................................................75 3.4 Reactivity of Hydroxyl Radical Addition to Toluene .......................................................78 3.5 Reactivity of Hydroxyl Radical Addition to Other Aromatics .........................................84 3.5.1 o-Xylene (1,2-Dimethylbenzene) ......................................................................................84 3.5.2 m-Xylene (1,3-Dimethylbenzene) .....................................................................................85 3.5.3 p-Xylene (1,4-Dimethylbenzene) ......................................................................................87 3.5.4 Anisole (Methoxybenzene) ...............................................................................................89 3.5.5 Chlorobenzene .................................................................................................................91 3.5.6 Trifluorotoluene (α,α,α-trifluoromethylbenzene) ................................................................93 CHAPTER 4 –HYDROXYL RADICAL REACTIONS IN ACETONITRILE: THE EFFECT OF SOLVENT ON RADICAL REACTIONS .................................................................................. 102 ii 4.1 Introductory Remarks ..................................................................................................... 102 4.2 Hydroxyl Radical Addition to Toluene (Methylbenzene) .............................................. 103 4.3 Hydroxyl Radical Addition to other Aromatic Substrates ............................................ 112 4.3.1 o-Xylene (1,2-Dimethylbenzene) .................................................................................... 112 4.3.2 m-Xylene (1,3-Dimethylbenzene) ................................................................................... 115 4.3.3 p-Xylene (1,4-Dimethylbenzene) .................................................................................... 119 4.3.4 Chlorobenzene ............................................................................................................... 120 4.3.5 Trifluorotoluene (α,α,α-Trifluoromethylbenzene) ............................................................. 124 4.4 Structure-Reactivity Relationships ................................................................................ 127 4.5 Preferential Addition of ·OH to ortho-Positions ............................................................ 131 CHAPTER 5 – CONCLUSIONS AND FUTURE EXPERIMENTATION ................................... 137 5.1 Introductory Remarks ..................................................................................................... 137 5.2 Future Exploration of ·OH Reactivity ............................................................................. 140 5.2.1 Continued Investigation of Arene Reactivity ................................................................... 140 5.2.2 Secondary Oxidation Products ....................................................................................... 143 5.2.3 Expansion of Solvent Effects .......................................................................................... 146 APPENDIX I – CALIBRATION CURVES OF STANDARDS................................................... 150 APPENDIX II – THERMAL DECOMPOSITION OF AZOHYDROPEROXIDE INITIATOR IN ACETONITRILE ....................................................................................................................
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