Imazamethabenz hydrolysis on oxide surfaces at several pH

Abstract

Imazamethabenz is used for postemergence control of wild oats and other weeds in wheat, barley, and sunflower. Imazamethabenz hydrolysis and the formation of the acid form, imazamethabenz acid, are necessary for herbicidal activity. The type of imazamethabenz acid adsorption on oxides affects its fate for herbicidal activity and persistence. Imazamethabenz hydrolysis with or without oxides and imazamethabenz acid adsorption to oxides were examined in aqueous buffer suspensions of aluminum oxide (Al2O3), goethite (FeOOH), amorphous silica (SiO2), and anatase (TiO 2) at several pH. Imazamethabenz hydrolysis rates in oxide-free solution followed first-order kinetics. Hydrolysis rate increased as pH increased, and exhibited a log-linear relationship with pH. Hydrolysis of imazamethabenz in oxide solutions also followed first-order kinetics. Some oxides increased the imazamethabenz hydrolysis rate at a given pH, but pH played a much greater role in increasing the hydrolysis rate of imazamethabenz than did oxides. Adsorption to oxides of imazamethabenz acid formed from imazamethabenz hydrolysis decreased as pH increased. At pH 5.0, acid adsorption to Al2O3 was 44% of the total acid product, while acid adsorption to Al2O3 was 6% of the total acid product at pH 8.0. ©Pesticide Science Society of Japan.