Objectives 1 and 2 have been completed and Objective 3 is approximately 70 percent completed. Because of a staffing issue, we have obtained a no-cost extension and will be continuing this project for a fourth year. Experiments with atrazine were conducted by varying the identity and concentration of the nucleophile, as well as solution pH, to verify that reactions were first-order in the reactive nucleophile concentration. A fluorinated analog of atrazine was synthesized, and its reactions were studied. Rate constants for reaction with polysulfides vary by seven orders of magnitude, and kHS - by at least five orders of magnitude.
Results indicate substitution of halogen by sulfur.
This QSAR indicated a weak correlation between LUMO energy and reactivity, no doubt reflecting its neglect of steric effects as well as the subtle effects of transition state structure on the rate of reaction. Better correlations were observed within individual classes of chloroazines than for chloroazines as a whole. To test the ability of laboratory-derived rate constants to predict haloazine fate in the much more complicated milieu of natural waters, several samples from a natural sulfidic lake water were fortified with sulfur and the pH was adjusted to produce varying concentrations of polysulfides. These modified waters were then allowed to react with atrazine. A sharp increase in reactivity was observed on increasing polysulfide concentration.