Publication Date

5-2012

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Chemistry

Department

Chemistry

Supervisory Committee Chair

Owen McDougal

Supervisory Committee Member

Gerry Chingas

Supervisory Committee Member

Dale Russell

Abstract

The hydrolysis reaction of parathion (PTH) to produce para-nitrophenolate (pNP) and O,O-diethylthiophosphate (DETP) was examined in a minimally disturbed liquid-liquid biphasic reaction system by proton and phosphorous nuclear magnetic resonance spectroscopy. The effect of the micellar cationic surfactant, cetyltrimethylammonium chloride (CTAC), on PTH transport, hydrolysis, and system characteristics including reactant-product concentrations, pNP partition coefficients, pNP surface activity, ultraviolet degradation of pNP, oxidation of pNP, and impurities in PTH are reported. Surfactant reaction systems resulted in a 2.5 order of magnitude increase in the amount of PTH transported into the aqueous layer as compared to the control system at 2100 h. A comparison between the total concentration of reaction products, pNP and DETP, in the control system without surfactant and in the presence of 33.3 mM CTAC varied by less than 5%. Interestingly, the total amount of pNP detected in the bulk organic and aqueous layers was five to six times lower than DETP, independent of surfactant. This apparent discrepancy in the concentration of pNP was investigated and was concluded to arise from an impurity present in the ampules of PTH. This impurity was disguised because the chemical shifts of DETP and PTH overlapped in deuterated chloroform. The impurities were revealed when the PTH was dissolved in deuterated benzene. The kinetics of the reaction between PTH and NaOD in absence of surfactant were also determined by running single phase experiments that were mixed before analysis at 0 mM NaOD, 5.33 mM NaOD, 33.33 mM NaOD, and 100 mM NaOD. An experiment at 100 mM DCl was also conducted to ensure that there was no acid hydrolysis occurring at room temperature. There was no reaction occurring at the 100 mM DCl or the 0 mM NaOD. The pseudo-first order rate for the 5.3 mM NaOD system was determined to be 1.9 x 10-4 (± 4 x 10-5) min-1. The 33.3 mM NaOD pseudo-first order rate was determined to be 1.4 x 10-3(± 2 x 10-4) min-1. The pseudo-first order rate for the 100 mM NaOD was determined to be 3.8 x 10-3 (± 4 x 10-4) min-1. When the pseudo-first order rate was plotted versus OD- concentration, the second order rate constant was determined to be 3.90 x 10-5 (± 8 x 10-7)mM-1min-1. The conclusion of this work is that CTAC facilitates transport of PTH, changes product solubility characteristics, and does not significantly enhance degradation of organophosphates. The reaction between PTH and NaOD in the absence of surfactant increased linearly, as expected, with respect to OD– concentration.

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