The Hydrolysis of 2,4‐dichlorophenoxy‐ Acetate Esters to 2,4‐dichlorophenoxyacetic Acid in Saskatchewan Soils

Summary. The hydrolysis of the iso‐propyl, n‐butyl and iso‐octyl esters of 2,4‐dichloro‐phenoxyacetic acid to the free acid was studied in aqueous solutions and on three prairie soils. The esters were analysed using electron‐capture gas chromatography following extraction from solution with benzene, and from soils, using either 10% aqueous aceto‐nitrile or a 2:1 mixture of benzene and iso‐propanol. Ester hydrolysis in 0·1 n sodium hydroxide solution was very rapid, more than 50% of all the esters being hydrolysed in less than 1 min. In 0·1 n sodium carbonate solution the times for 50% hydrolysis at 25°C were < 5, 5 and 30 min for the n‐butyl, iso‐propyl and iso‐octyl esters respectively. In distilled water negligible hydrolysis occurred over a 5 h period. The iso‐propyl and n‐butyl esters underwent a very facile hydrolysis on soils. Shaking the treated soils with 0·1 M calcium chloride solution for 30 min at 25°C resulted in extensive hydrolysis to the acid as determined spectrophotometrically. Under similar conditions negligible hydrolysis of the iso‐octyl ester occurred. After 1·5 h at 25±1°C on soils at their wilting point moisture levels, and greater, less than 15% of the applied iso‐propyl or n‐butyl esters could be recovered using either extraction procedure, indicating rapid hydrolysis to the acid. After 24 h no iso‐propyl or n‐butyl ester residues could be detected in any of the soils. Loss of the iso‐octyl ester was slower under these conditions with approximately 20–30% of the ester remaining after 24 h, and 10% after 48 h. L'hydrolyse des esters de 2,4 dichlorophénoxyacétates en acide 2,4 dichlorophénoxyacétique dans les sols du saskatchewan.