Abstract A comparative study of the reaction of catalytic epoxidation of cyclohexene with hydrogen peroxide in water and ionic liquids containing dihydrogen phosphate anions, such as trimethylammonium dihydrogen phosphate, diethylammonium dihydrogen phosphate, and N-methylpyrrolidonium dihydrogen phosphate has been performed. It has been shown that as high a cyclohexane epoxide yield as 80% with a selectivity close to quantitative ...