The reported uncatalyzed hydrolysis half-life of 1800 years at a pH of 6.97 The half-life for the latter compound is much shorter than Resulting half-lives range from < 1 minute (for anilazine) to approximately 4ĭays (for atrazine). (reported for salt marsh sediment porewaters at pH 7.1 Boulegue, 1982). Laboratory-derived rate constants for haloazines were extrapolated to anĮnvironmentally relevant concentration of hydrogen sulfide and polysulfides Observed within individual classes of chloroazines than for chloroazines as a Transition state structure on the rate of reaction. This QSAR indicated a weak correlation between LUMO energy and reactivity, noĭoubt reflecting its neglect of steric effects as well as the subtle effects of Provide a useful tool for predicting the environmental fate of untested azines. Reactivity to calculated LUMO energies was developed in the hope it might Structure-reactivity trends observed, are all consistent with a nucleophilicĪromatic substitution (SNAr) reaction mechanism.Ī quantitative structure-activity relationship (QSAR) comparing chloroazine The products, the first-orderĭependence on the concentration of the nucleophile, and the qualitative Indicate substitution of halogen by sulfur. Iodide or pentafluorobenzyl bromide, followed by GC/MS/EI analysis. Products were identified by derivatization with methyl Polysulfides vary by seven orders of magnitude, and kHS - by at leastįive orders of magnitude. For example, atrazine is recalcitrant to reaction with Versus HS - were observed, with ratios of kS n 2-/kHS- ranging from 75 to more Large differences in the reactivity of haloazines toward polysulfide dianions Heterocycles), were found to confer increased reactivity. Moreover, ringĪza nitrogens, as well as the presence of a fused ring system (bicyclic Number of chlorine substituents resulted in increased reactivity. For the reactions ofĬhloroazines with HS - and S n 2-, a general trend was observed in which an increasing Was synthesized, and its reactions were studied. Quinoxaline compounds also were investigated. Reactions of HS - and S n 2- with seven halogenated pyridine, pyrimidine, and To provide information pertinent to the fate of reactive dye compounds, That reactions were first-order in the reactive nucleophile concentration. Identity and concentration of the nucleophile, as well as solution pH, to verify Experiments with atrazine were conducted by varying the Polysulfide dianions and HS - species were determined in aqueous Rates of reaction of three commonly used chloro-s-triazine agrochemicals with Have been completed and Objective 3 is approximately 70 percent completed.īecause of a staffing issue, we have obtained a no-cost extension and will beĬontinuing this project for a fourth year. This report covers the third year of a 3-year project. We hypothesize that reactions in sulfidic hydrologic environments between well-defined reduced sulfur species (particularly polysulfide ions and aromatic thiolate moieties present in NOM and chloro-s-triazine herbicides, fungicides, and reactive dye compounds may provide a significant sink for such organic contaminants. The objectives of this research are to: (1) determine the rates of abiotic reactions of triazines (and related species) with inorganic reduced sulfur nucleophiles (2) examine the ability of azines to bind covalently to natural organic matter (NOM) and (3) examine the potential impact of reduced sulfur species on the fate of azines in anoxic coastal marine environments. Institution: The Johns Hopkins UniversityĮxploratory Research - Environmental Chemistry (1997) Title: Role of Reduced Sulfur Species in Promoting the Transformation of Triazines in Estuaries and Salt Marshes 2000 Progress Report: Role of Reduced Sulfur Species in Promoting the Transformation of Triazines in Estuaries and Salt Marshes EPA Grant Number: R826269
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