AGRO 7 |
| The chlorinated fumigants chloropicrin and 1,3-dichloropropene (1,3-D) are extensively used to control soilborne pests. Transformation of these two pesticides by hydrogen sulfide species (H2S and HS-) was examined in well-defined anoxic aqueous solutions. Chloropicrin underwent an extremely rapid redox reaction in the hydrogen sulfide solution. Transformation products indicated reductive dechlorination of chloropicrin by hydrogen sulfide species to produce dichloro- and chloronitromethane. For 1,3-D, kinetics and transformation products analysis revealed that the reaction between 1,3-D and hydrogen sulfide species is an SN2 nucleophilic substitution process, in which the chlorine at C3 of 1,3-D is substituted by the sulfur nucleophile to form corresponding mercaptans. The transformation of chloropicrin and 1,3-D in hydrogen sulfide solution significantly increased with increasing pH, suggesting that the reactivity of hydrogen sulfide species stems primarily from HS-. Because of the relatively low smell threshold values and potential persistence of organic sulfur products, the environmental behaviors of transformation products of 1,3-D and HS- need be assessed. |
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Agrochemical Residue & Metabolism Chemistry
8:30 AM-11:30 AM, Sunday, 10 September 2006 San Francisco Marriott -- Salon 1, Oral
Division of Agrochemicals |