A computational study on the reaction mechanism of C2H5S with HO2

► The reaction mechanism of C2H5S with HO2 was studied using DFT and CC approaches. ► The reaction scheme was designed on the basis of Mulliken atomic spin densities. ► Eleven singlet and triplet reaction channels for the title reaction were explored. ► The addition-elimination R4 and direct hydrogen abstraction reaction R5 are likely competitive.