Hydrolysis kinetics of the monophosphate ester triclofos sodium

The hydrolysis kinetics of the monophosphate ester triclofos sodium were studied in the pH 0.00--7.80 range, the 80.1--98.4 degrees range, and ionic strengths of 0.02--1.50. The pK1 and pK2 values for triclofos were 1.00 +/- 0.05 and 5.80 +/- 0.05, respectively. The pH dependency observed was consistent with a theory in which the hydrolysis rates of the triclofos species follow the order: monoanion greater than unionized greater than dianion. The apparent first-order rate constants at 80.1 degrees associated with each species were 6.4 +/- 0.6 X 10(-3), 28.0 +/- 0.5 X 10(-3), and 0.3 +/- 0.1 hr-1, respectively, Different Arrhenius activation energies were observed at pH 0.00, 3.50, and 7.80, at which values the unionized, monoanion, and dianion forms were the dominant species present, respectively. The reaction showed a modest positive kinetic salt effect at pH 3.50 and a modest negative effect at pH 7.80. Various mechanistic possibilities are discussed.