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Determining Reaction R ates of N itroaromatic Reduction Reactions

Determining Reaction R ates of N itroaromatic Reduction Reactions . Hayley Johnston Mentor: Ali Salter-Blanc Tratnyek Lab Summer 2013. Background . Release of energetic munitions compounds into the environment leads to contamination Water Soil Sediments

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Determining Reaction R ates of N itroaromatic Reduction Reactions

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  1. Determining Reaction Rates of Nitroaromatic Reduction Reactions Hayley Johnston Mentor: Ali Salter-Blanc TratnyekLab Summer 2013

  2. Background • Release of energetic munitions compounds into the environment leads to contamination • Water • Soil • Sediments • Selection of new energetic compounds • Less shock sensitive (safer) • Toxicity • Environmental persistance

  3. Objectives • Determine the reaction rate of various nitroaromatic compounds in reducing conditions • Formulate quantitative structure activity relationships (QSARs) • Predict the behavior of current and future ammunitions contaminants in the environment nitrobenzene 2,4-dinitroanisole 2,4,6-trinitrotoluene 2,4-dinitrotoluene 4-chloro-1-nitrobenzene 1,3-dinitrobenzene

  4. Reduction of Nitroaromatic Compounds (NACs) • Reduction: an electron transfer reaction where the product gains electrons • Overall Reaction • 1st Step • Reduction by electron shuttle (mediator) High rate Moderate rate

  5. Kinetics • Generally assumed to be pseudo-first-order • Reaction is second order in [Fe(II)P] and [NAC] rate= kFeP[Fe(II)P][NAC] • [Fe(II)P] is constant so it can combine with the kFeP to get the kobs rate= kobs [NAC] • Obtain second order rate constant (kFeP) from • kobs =kFeP [FeP]

  6. Methods • 60mL Reaction Vial containing: • 25-400μL of 4.29mM iron(III) porphine (FeP) • 1mL of 0.25M cysteine (to generate Fe (II)) • 49mL Sodium Phosphate Buffer pH 7.0 • 50μL 0.1M nitroaromatic compound (NAC) • 25O water bath • HPLC detection @ 254nm or 220nm • Sampling frequency based on half life of NAC

  7. Reduction Rates of 2,4-dinitrotoluene (DNT) by increasing concentrations of FeP Slope values are the observed reaction rate (kobs) for each reaction The kobs values are plotted against the concentration of FeP to obtain the kFePvalue of each NAC

  8. Complications • New fit parameters • Autocatalytic reaction? A→B A+B→C

  9. Results • First order fit is good up until ≈10μM NAC • This enables me to obtain second order rate constants for each compound

  10. Acknowledgements I would like to extend many thanks to: Ali Salter-Blanc Paul Tratnyek Vanessa Green Oregon Health and Science University (OHSU)

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