Effect of positional isomerism on the abiotic degradation of pesticides: Case of m- and p-imazamethabenz-methyl

• Published in: Chemosphere (Oxford) Vol. 68; no. 3; pp. 464 - 471
• Main Authors: Brigante, Marcello, Emmelin, Corinne, Ferronato, Corinne, Greca, Marina Della, Previtera, Lucio, Paisse, Jean Olivier, Chovelon, Jean-Marc
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2007; Elsevier
• Subjects: Abiotic degradation; Applied sciences; Benzoates - chemistry; Biological and physicochemical properties of pollutants. Interaction in the soil; Catalysis; catalysts; Chemical Sciences; degradation products; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment and Society; Environmental Sciences; Exact sciences and technology; free radicals; Herbicides - chemistry; high performance liquid chromatography; HPLC; hydroxyl radical; imazamethabenz; Imidazoles - chemistry; Imidazolinone; isomers; Light; m-imazamethabenz; Molecular Structure; p-imazamethabenz; Pesticides; photochemical reactions; Photodegradation; photolysis; Pollution; Pollution, environment geology; Soil and sediments pollution; Time Factors; titanium dioxide; Photodegradation; Imidazolinone; Abiotic degradation; Pesticides; Imidazolinone; Photodegradation; Abiotic degradation; Pesticides; Pollutant behavior; Imidazolinone derivatives; Agricultural soil; Chemical degradation; Soil pollution; Herbicide; Hydrolysis; Position isomer; Selfpurification; Reaction mechanism; Agriculture; Property structure relationship; Degradation product; HPLC; Organic compounds; Photochemical degradation; "HPLC"; "Pesticides"; "Photodegradation"; "Imidazolinone"; "Abiotic degradation"
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2006.12.084

The effect of positional isomerism on chemical and photochemical degradations of the Imazamethabenz-methyl (IMBM), a pesticide of the imidazolinone family, has been studied. IMBM is proposed in the form of a mixture of the two positional isomers: meta and para. The development of an effective HPLC method (resolution factor R = 1.3) allows us to follow either the abiotic disappearance of the meta and para IMBM and the formation of their breakdown products. The abiotic degradation studies include the chemical hydrolysis, as well as the direct and the indirect photodecomposition. We used TiO 2, a well-known initiator of hydroxyl radicals, to highlight the role of OH in the indirect photodegradation. This work confirms the different behaviours of positional isomers in the environment. Indeed the chemical or direct photochemical degradation is faster for the meta isomer than for the para. Whereas, concerning IMBM, there is not any prevalent influence of this type of isomerism on the indirect photochemical degradation. The degradation products were tentatively identified by LC-MS, NMR and IR and a degradation pathway was proposed.