Investigation of Water-Molecule Complexes and Their Catalytic Effect on Important Atmospheric Reactions
This dissertation is a collection of works that investigates issues related to environmental chemistry. The first portion of this research explores the role of water vapor on the kinetics of important atmospheric reactions. Work is presented on the self-reaction of β-hydroxyethyl peroxy radical (β-HEP) and the catalytic increase in reaction rate by water vapor. β-HEP serves as a model system for investigating the possible role of water vapor in perturbing the kinetics and product branching ratio of atmospheric reactions of other alkyl peroxy radicals. The self-reaction rate coefficient of Î²-HEP was investigated between 276-296 K with 1.0 × 10^15 to 2.5 × 10^17 molecules cm^-3 of water vapor at 200 Torr total pressure by slow-flow laser flash photolysis coupled with UV time-resolved spectroscopy and long-path, wavelength-modulated, diode-laser spectroscopy. The overall disproportionation rate constant is expressed as the product of temperature-dependent and water vapor-dependent terms giving k(T,H2O) = 7.8 × 10^-14 (e^8.2 ^(±2.5) ^kJ/RT)(1 + 1.4 × 10^-34 × e^92 ^(±11) ^kJ/RT[H2O]). The results suggest that formation of a β--HEP-H2O complex is responsible for the observed water vapor enhancement of the self-reaction rate coefficient. Complex formation is supported with computational results identifying three local energy minima for the β--HEP-H2O complex. Both the temperature range and water vapor concentrations used were chosen because of their significance to conditions in the troposphere. As the troposphere continues to get warmer and wetter, more complexes with water will form, which in turn may perturb the kinetics and product branching ratios of atmospheric reactions. Future studies are proposed for the reaction of Î²-HEP + NO leading to NO2 formation. A laser-induced fluorescence cell was designed, built, and tested in preparation for studies of NO2 formation. Additionally Harriott-cell optics were manufactured and tested to detect HO2 using two-tone frequency-modulated diode-laser spectroscopy. In a related work, the breakdown of the environmental contaminants polychlorinated biphenyls (PCB's) was investigated using a new method. A new method for analyzing anaerobic digestion is also presented. The degradation rate and efficiency of digestion processes are typically measured by introducing a substrate or pollutant into a digester and then monitoring the effluents for the pollutant or substrate, a costly and slow process. A new method for rapid measurement of the rates and efficiencies of anaerobic degradation of pollutants and lignocellulose substrates from various pretreatments is described. The method uses micro-reactors (10-30 mL) containing a mixed culture of anaerobic bacteria obtained from a working anaerobic digester. The rates of degradation and metabolism of pollutants are measured in parallel sets of micro-reactors. Measurements of metabolic rate and pollutant degradation simultaneously is an effective means of rapidly examining pollutant degradation on a micro-scale. Calorimetric measurements alone allow rapid, relative evaluation of various substrate pretreatment methods. Finally calorimetric and electrophoretic methods were used to further knowledge in analytical techniques applied to important problems. In the last section of this dissertation the thermal and photolytic breakdown of promethazine hydrochloride is reported. Promethazine hydrochloride is a mediation that is commonly used as an antihistamine, a sedative, and an antiemetic, and to treat motion sickness. Perivascular extravasation, unintentional intra-arterial injection and intraneuronal or perineuronal infiltration may lead to irreversible tissue damage if the drug is not properly diluted or is administered too quickly. Data on the stability of promethazine hydrochloride diluted in sodium chloride 0.9% are lacking. This study evaluates the thermal and photolytic degradation of promethazine hydrochloride concentrations of 250 µg/mL and 125 µg/mL diluted in sodium chloride 0.9% over a period of 9 days. Degradation rates of promethazine hydrochloride were determined under UV-light, fluorescent light, and no light at various temperatures and concentrations to determine medication stability. The shelf-life (<10% degradation) at 25°C under normal fluorescent lights is 4.9 days, at 25°C protected from light, 6.6 days, and at 7°C in the dark, 8.1 days. These results may increase patient safety by improving current protocols for intravenous promethazine administration
College and Department
Physical and Mathematical Sciences; Chemistry and Biochemistry
BYU ScholarsArchive Citation
Cline, Taylor Scott, "Investigation of Water-Molecule Complexes and Their Catalytic Effect on Important Atmospheric Reactions" (2013). Theses and Dissertations. 3990.
peroxy radical, radicals, water enhancement, atmospheric chemistry, spectroscopy, uv-vis, frequency modulated spectroscopy, gas-phase kinetics