title: Hydrolytic Activation Kinetics of the Herbicide Benzobicyclon in Simulated Aquatic Systems.
abstract: Herbicide resistance is a growing concern for weeds in California rice fields. Benzobicyclon (BZB; 3-(2-chloro-4-(methylsulfonyl)benzoyl)-2-phenylthiobicyclo[3.2.1]oct-2-en-4-one) has proven successful against resistant rice field weeds in Asia. A pro-herbicide, BZB forms the active agent, benzobicyclon hydrolysate (BH), in water; however, the transformation kinetics are not understood for aquatic systems, particularly flooded California rice fields. A quantitative experiment was performed to assess the primary mechanism and kinetics of BZB hydrolysis to BH. Complete conversion to BH was observed for all treatments. Basic conditions (pH 9) enhanced the reaction, with half-lives ranging from 5 to 28 h. Dissolved organic carbon (DOC) hindered transformation, which is consistent with other base-catalyzed hydrolysis reactions. BH was relatively hydrolytically stable, with 18% maximum loss after 5 days. Results indicate BZB is an efficient pro-herbicide under aqueous conditions such as those of a California rice field, although application may be best suited for fields with recirculating tailwater systems.
authors.affiliation: Department of Environmental Toxicology, College of Agricultural and Environmental Sciences, University of California , One Shields Avenue, Davis, California 95616, United States.
authors.forename: Katryn L
authors.initials: KL
authors.lastname: Williams
authors.affiliation: Department of Environmental Toxicology, College of Agricultural and Environmental Sciences, University of California , One Shields Avenue, Davis, California 95616, United States.
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Tjeerdema
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000737:chemistry*; D002140:California; D006540:Herbicides / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D015394:Molecular Structure; D012275:Oryza / Q000254:growth & development; D057685:Plant Weeds / Q000187:drug effects* / Q000254:growth & development; D013450:Sulfones / Q000737:chemistry*; D014867:Water / Q000032:analysis; D058728:Weed Control
chemical_list: D001643:Bridged Bicyclo Compounds; D006540:Herbicides; D013450:Sulfones; C000603422:benzobicyclon; D014867:Water
keywords: Butte; Show-Ace; benzobicyclon; herbicide; hydrolysis; pesticide; rice