Role of acidic ligand for clean synthesis of adipic acid via catalytic oxidation of cyclohexene

The effects of ligands on clean synthesis of adipic acid via direct oxidation of cyclohexene with 3096 H2O2 catalyzed by Na(2)W0(4) . 2H(2)O were studied. In most cases, the yield of target product adipic acid is high if the acidity of ligand is strong. Although the acidity of some phenolic ligands, L(+)ascorbic acid and 8-quinolinol is weak, the yield of adipic acid is still high. It is demonstrated that the acidic effect and the coordination effect of ligand play the same important role in oxidaton of cyclohexene with 30 % H2O2 to adipic acid catalyzed by Na2WO4 . 2H(2)O. The experimental results for acidic ligand amount and reaction kinetics show that the hydrolysis of cyclohexene oxide to 1,2-cyclohexandiol is a critical step and the acidity of the reaction system is necessary.