The reactions of imidazolium-based ionic liquids having different substituent groups on the ring with hydrated electrons (eaq-),hydroxyl radicals (·OH),and sulfate anion radicals (SO4·-) were investigated using nanosecond pulse radiolysis techniques.The spectra of these ionic liquids on reaction with eaq-all exhibited a similar peak at about 320 nm,and a typical peak for eaq-in aqueous ionic liquid solutions.The reaction rate constants for 1,3-disubstituted imidazolium-based ionic liquid hexafluorophosphates (BMIPF 6) with eaq-were deduced to be 10 10 L mol-1s-1,however the values were lower for trisubstituted ionic liquids.For example,the rate constant for 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMMIBF 4) was 5.5×10 9 L mol-1s-1.Imidazolium-based ionic liquids reacted with hydroxyl radicals via adducts to produce a mixture of isomeric OH adducts,and the pk a value of the OH adducts was deduced to be 8.4±0.4 for 1-butyl-3-methylimdazolium tetrafluoroborate (BMIBF 4).Moreover,imidazolium cations were also oxidized by SO4·-to produce bivalent cation radicals,which exhibit a peak at 320 nm,and these rate constants are of the same order of magnitude,i.e.,10 9 L mol-1s-1,except that for 1-(2-hydroxyethyl)-3-methylimdazolium tetrafluoroborate with SO4·-(k=2.8×10 8 L mol-1 s-1).Theoretical calculations were carried out to estimate the structures of the products of reduction by eaq- and the results were related to the experimental data. The reactions of imidazolium-based ionic liquids having different substituent groups on the ring with hydrated electrons (eaq -), hydroxyl radicals (· OH), and sulfate anion radicals (SO4 · -) were investigated using nanosecond pulse radiolysis techniques. Spectra of. these ionic liquids on reaction with eaq-all exhibited a similar peak at about 320 nm, and a typical peak for eaq-in aqueous ionic liquid solutions. The reaction rate constants for 1,3-disubstituted imidazolium-based ionic liquid hexafluorophosphates (BMIPF 6 However, the values ​​were lower for trisubstituted ionic liquids.For example, the rate constant for 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMMIBF 4) was 5.5 × 10 9 L mol-1s-1.Imidazolium-based ionic liquids reacted with hydroxyl radicals via adducts to produce a mixture of isomeric OH adducts, and the pk a value of the OH adducts was deduced to be 8.4 ± 0.4 for 1-butyl -3-methylimdazolium tetrafluoroborate (BMIBF 4) .More over, imidazolium cations were also oxidized by SO 4 · -to produce bivalent cation radicals, which exhibit a peak at 320 nm, and these rate constants are of the same order of magnitude, ie, 10 9 L mol-1s-1, except that for the 1- (2-hydroxyethyl) -3-methylimdazolium tetrafluoroborate with SO 4 · (k = 2.8 × 10 8 L mol -1 s -1) .Theoretical calculations were carried out to estimate the structures of the products of reduction by eaq- and the results were related to the experimental data.