Rates of hydrolysis of a monochlorotriazine dye in presence of non-ionic surfactant

Abstract

The presence of nonylphenol-poly(oxyethylene) surfactant decreases the rate constant for the hydrolysis of a monochlorotriazine dye, the effect being enhanced by increasing the surfactant to dye ratio and diminishing by increasing the temperature. At 80º and 100º, the longer the ethylene oxide chain length of a surfactant the more effective it is in reducing the rate constant. At 60°, however, all of the surfactants used appear to be equally effective. At 80º and 100º, extrapolation of rate constants to zero surfactant to dye ratio gives a value very close to the rate constant in the absence of surfactant, but at 60º the rate constant for NPl0 extrapolated to zero surfactant to dye ratio is close to the value from the surfactant-free run, but values obtained with the other surfactants are much higher and similar to that obtained in presence of a polyether glycol. It is suggested that this anomaly is due to the initial aggregation of the dye at 60° so that the addition of small quantities of surfactant other than NPl0 causes initial disaggregation and an increase in the rate of hydrolysis. Further increases in the amount of surfactant cause dye-surfactant complex formation which produces a decrease in the rate of hydrolysis.