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.
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.