One-step conversion of benzene to phenol in plasma-irradiated benzene solution

One-step synthesis of phenol was achieved in aqueous benzene solutions irradiated with atmospheric-pressure air and helium plasmas. We prepared the plasma-irradiated benzene solution by two experimental procedures: (1) mixture solution of benzene and NaCl was irradiated with the plasma and (2) benzene was admixed with the NaCl solution irradiated with the plasma. We observed the synthesis of phenol in both the methods except in procedure (2) using the helium plasma. When we used air for discharge, we observed the continuous production of phenol for at least 300 h after the irradiation of the plasma or mixing benzene with plasma-irradiated NaCl solution. The synthesis of phenol is attributed to the substitution reaction of hydroxyl radical (∙OH) with a hydrogen in benzene, which has been confirmed by the relationship between the synthesis rate of phenol and the concentration of a scavenger (2-propanol) for ∙OH. The apparent long lifetime of ∙OH is owing to its continuous production in the solution by homolytic splitting of ONOOH, which is produced from H2O2 and NO2−.