Hydrolysis of Azinphosmethyl Induced by the Surface of Smectites
The effect of layer charge and of the interlayer cations of smectites on the hydrolysis of azinphosmethyl (0,0-dimethyl S-((4-oxo-l,2,3-benzotriazine-3(4H)-yl)methyl) phosphorodithioate) in an aqueous medium was investigated. Ultraviolet spectroscopy was used for monitoring the hydrolysis process. Hydrolysis of the pesticide is catalyzed by Ca-hectorite (layer charge 0.216) but is not catalyzed by Ca-nontronite nor by Ca-montmorillonites with a layer charge above 0.216. The Mg- and Cu-hectorites and Cu-montmorillonite with a layer charge of 0.264 also show catalytic activity. The catalytic activities of the Ca2+ and Cu2+ cations as exchange cations of the smectite and as salts are compared. In agreement with previously reported work, the results show that the hydrolysis of azinphosmethyl may involve the adsorption of the pesticide into the interlayer space of the smectites, forming a bidentate complex with the interlayer cations. This interaction must enhance the electrophilic nature of the phosphorus atom, thereby facilitating its nucleophilic attack by the OH” ion and producing rupture of the P-S bond.
Key WordsHydrolysis Adsorption Azinphosmethyl Smectite Organophosphorus pesticides
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- American Petroleum Institute (1950) Research Project 49. Clay Minerals Standard: Preliminary Reports 1–8: Columbia University, New York.Google Scholar
- Eto, M. (1974) Organophosphorus Pesticides: Organic and Biological Chemistry: CRC Press, Inc., Cleveland, Ohio, 57–121.Google Scholar
- González-García, F. and González-García, S. (1953) Modificaciones producidas por tratamiento térmico en las propiedades fisicoquimicas de los silicatos de la série isomorfa montmorillonita-beidellita: An. Edafol. Agrobiol. 12, 925–992.Google Scholar
- Gutiérrez-Ríos, E. and González-García, F. (1949) Génesis de la Montmorillonita de Marruecos español: An. Edafol. Agrobiol. 8, 537–547.Google Scholar
- Hance, R. J. (1970) Influence of sorption on the decomposition ofpesticides. Sorption and transport processes in soils. SCI monograph 37: Academic Press, New York, 92–107.Google Scholar
- Melnikov, N. N. (1971) Chemistry of pesticides: Res. Rev. 36, 371–372.Google Scholar
- Theng, B. K. J. (1974) The Chemistry of Clay-Organic Reactions: Wiley, New York, 26–281.Google Scholar
- Worthing, C. R. and Walker, S. B. (1987) The Pesticide Manual. A World Compendium: The La venham Press Ltd., Lavenham, England, 41–42.Google Scholar