Enantioselective transformation of the herbicides diclofop‐methyl and fenoxaprop‐ethyl in soil

The separate enantiomers of diclofop‐methyl and fenoxaprop‐ethyl were incubated with two soils under aerobic conditions. Rapid hydrolysis to the corresponding acids diclofop and fenoxaprop was observed. At various time intervals after soil treatment the parent compound and its free acid were extracted and the extracts were investigated by high‐performance liquid chromatography. The determination of the K:S‐ratio using a chiral stationary phase revealed that no racemisation of the esters took place. However, inversion of the hydrolysis products was observed. In both soils the acids with the S‐configuration showed a significantly higher inversion tendency than the acids with the R‐configuration. In one soil the S‐acids of both herbicides were inverted (50% inversion in 4–7 days) to yield, ultimately, a residue containing 70% R‐ and 30% S‐enantiomer.