Decomposition of halophenols in room-temperature ionic liquids by ionizing radiation

In this article, we report the reaction of halophenols with solvated electrons in room-temperature ionic liquids (RTILs) initiated by γ-ray and pulsed electron radiolyses. The decomposition G-values of ortho-chlorophenol (CP) in N-methyl-N-propylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (TFSI), N-butyl-N-methylpyrrolidinium-TFSI and N-methyl-N-propylpiperidinium-TFSI were estimated to be 1.4, 1.6, and 1.7 molecules 10-2 eV-1 under γ-ray irradiation; these values were almost the same as the yield of solvated electron formation. The second-order rate constant for the reaction of CP with solvated electrons in diethylmethyl(2-methoxyethyl)ammonium (DEMMA)-tetrafluoroborate (BF4) was one order of magnitude lower than that in DEMMA-TFSI although the G-values of CP decomposition and phenol formation in DEMMA-BF4 were higher. The decomposition yield of ortho-iodophenol in DEMMA-TFSI was slightly higher than that of the other halophenol (ortho-fluorophenol, CP, and ortho-bromophenol), and the formation yield of phenol for the decomposition of only ortho-fluorophenol was lower.