Kinetics of aqueous base and acid hydrolysis of aldicarb, aldicarb sulfoxide and aldicarb sulfone

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Abstract
The kinetics of degradation of aqueous solutions of aldicarb [insecticide], aldicarb sulfoxide and aldicarb sulfone by base hydrolysis were investigated. Pseudo 1st order rate constants of 37 .mu.g/l solutions were determined at different hydroxide concentrations by acid-base titration. Second order rate constants were calculated, and aldicarb sulfone was more sensitive to hydroxide ion concentration than aldicarb sulfoxide which was more sensitive than aldicarb. Temperature effects were determined by measuring the base hydrolysis rate constant for aldicarb sulfone at 5.degree., 15.degree., 20.degree., 25.degree., 30.degree. and 35.degree. C. An activation energy of 15.2 .+-. 0.1 kcal/mol was calculated. Addition of neutral electrolyte decreased the rate constant for base hydrolysis. Acid catalyzed hydrolysis rate constants were also measured for aldicarb sulfone, and the reaction was slower. The 2nd order (reaction) rate constant for base hydrolysis of aldicarb sulfone was 40.3 (.+-. 05) l mol-1 min-1; for acid catalyzed hydrolysis it was 7.33 (.+-. 0.06) .times. 10-4 l mol-1 min-1.