Abstract |
The hydrolysis kinetics of 4-chlorostibene oxide (CSO) in buffered distilled water, in natural waters, and in sediment associated water are reported. The disappearance of CSO followed pseudo-first-order kinetics in buffered water over the experimental pH range of 3 to 11. Below pH 5, acid-catalyzed hydrolysis dominates, with a second-order rate constant of 11.3 (+ or - 1.0)/M min. Above pH 5, hydrolysis is independent of pH, with a rate constant of 1.02 (+ or - 0.12)X 10 sup -4 min sup -1 at 25 C. In natural waters, the hydrolysis rate constant of CSO had an average value of 0.59 (+ or - 0.12) X 10 sup -4 min sup -1. In sediment-associated water, the observed rate constant was 1.70 (+ or - 0.05) X 10 sup -4 min sup -1. Sorption of CSO to the humic materials in natural waters and biotic effects in sediment-associated water appropriately explain the differences from sterile buffer solutions. Buffer catalysis was observed, but on the other hand, a negative ionic strength affect was determined. The formation of diastereoisomers of 1-(4-chlorophenyl)-2-phenylethylene glycol as major products at both acidic and neutral pH values suggests that CSC undergoes acid-catalyzed as well as neutral hydrolysis reactions through an A-1 carbonium ion mechanism. (Copyright (c) 1989 SETAC.) |