KINETIC STUDY OF REVERSIBLE CONVERSION OF METHYL 1-(BUTYLCARBAMOYL)-2-BENZIMIDAZOLECARBAMATE (BENOMYL) TO METHYL 2-BENZIMIDAZOLECARBAMATE (MBC) AND NORMAL-BUTYL ISOCYANATE (BIC) IN ORGANIC-SOLVENTS

The decomposition of benomyl (B), methyl l-(butylcarbamoyl)-2-benzimidazolecarbamate, in chloroform, dichloromethane, ethyl acetate, benzene, ethanol, methanol, and dioxane was studied spectrophotometrically at 25 °C. The mechanism of decomposition in all the solvents is represented by: B (k21) ⇄ MBC + BIC (k12) where MBC is methyl 2-benzimidazolecarbamate and BIC is n-butyl isocyanate. Values of the specific rates k12 and k2l have been obtained for all the solvents studied. The values of k12 show no correlation with existing solvent parameters, but k21 values seem to be larger for less polar solvents. Kinetic and spectrophotometric evidence for the establishment of equilibrium has been obtained and the values of the equilibrium constant K seem to be larger for more polar solvents. Also, the largest value of the percentage of intact benomyl at equilibrium is found for benzene while the smallest value is found for methanol. The significance of these kinetic studies to the meaningful analysis of benomyl is discussed. © 1978, American Chemical Society. All rights reserved.