Quantitative structure-transformation relationships of sulfonylurea herbicides

• Published in: Pest management science Vol. 58; no. 7; pp. 724 - 735
• Main Authors: Berger, Bernhard M, Müller, Martin, Eing, Andreas
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.07.2002; Wiley
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; buffers; descriptors; Fundamental and applied biological sciences. Psychology; Geologic Sediments - chemistry; Herbicides - chemistry; Hydrogen-Ion Concentration; Linear Models; Models, Chemical; Quantitative Structure-Activity Relationship; quantitative structure-transformation relationships; sediments; Soil; Soil and water pollution; Soil science; Sulfonylurea Compounds; sulfonylureas; Time Factors; Electronic properties; Chemical transformation; Polarizability; Pollutant behavior; Pesticides; Lipophily; Electron delocalization; Forecast model; Sediments; Reaction rate; Herbicide; Multiple regression; Hydrolysis; Soils; Biotransformation; Environment impact; Sulfonylureas; Reaction mechanism; pH; Descriptor; Property structure relationship; Chemical reactivity
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.519

Model development to predict transformation of sulfonylureas in different matrices was carried out using multiple linear regression. Descriptors for lipophilicity and molecular topology, as well as quantum chemical descriptors for energy, geometry, polarity, charges and reactivity using MOPAC with three different Hamiltonians, AM1, PM3 and MNDO, were calculated. In addition, experimental descriptors were measured and taken from the literature. End‐points were transformation rates of twelve sulfonylurea herbicides in buffers at different pH (4, 7 and 10), in sterile and native sediments, and in sterile and native soil. Inter‐correlation of reaction rates indicated four different groups of transformation types, for which sum parameters were calculated. (1) Hydrolysis at pH 4 could be estimated with pKa and charges at a specific atom of the heterocycle. (2) Hydrolysis at pH 7 and 10, as well as transformation in sterile sediments and soil, could be described with descriptors for reactivity (polarisability and superdelocalisability) at specific atoms of the molecules. (3) For transformation in native sediments different models could be found, all based on descriptors for polarisability, superdelocalisability and charges at specific atoms. (4) Modelling of biotransformation in native soil led to diverse models with a variety of descriptors reflecting electronic properties and lipophilicity. Models confirmed previous findings on reaction mechanisms and thereby prove valuable not only for quantitative prediction of reaction rates, but also for studies on transformation pathways. © 2002 Society of Chemical Industry