title: Catalytic Hydroxylation of Benzene to Phenol by Dioxygen with an NADH Analogue.
abstract: Hydroxylation of benzene by molecular oxygen (O2 ) occurs efficiently with 10-methyl-9,10-dihydroacridine (AcrH2 ) as an NADH analogue in the presence of a catalytic amount of Fe(ClO4 )3 or Fe(ClO4 )2 with excess trifluoroacetic acid in a solvent mixture of benzene and acetonitrile (1:1 v/v) to produce phenol, 10-methylacridinium ion and hydrogen peroxide (H2 O2 ) at 298 K. The catalytic oxidation of benzene by O2 with AcrH2 in the presence of a catalytic amount of Fe(ClO4 )3 is started by the formation of H2 O2 from AcrH2 , O2 , and H(+) . Hydroperoxyl radical (HO2 (.) ) is produced from H2 O2 with the redox pair of Fe(3+) /Fe(2+) by a Fenton type reaction. The rate-determining step in the initiation is the proton-coupled electron transfer from Fe(2+) to H2 O2 to produce HO(.) and H2 O. HO(.) abstracts hydrogen rapidly from H2 O2 to produce HO2 (.) and H2 O. The Fe(3+) produced was reduced back to Fe(2+) by H2 O2 . HO2 (.) reacts with benzene to produce the radical adduct, which abstracts hydrogen from AcrH2 to give the corresponding hydroperoxide, accompanied by generation of acridinyl radical (AcrH(.) ) to constitute the radical chain reaction. Hydroperoxyl radical (HO2 (.) ), which was detected by using the spin trap method with EPR analysis, acts as a chain carrier for the two radical chain pathways: one is the benzene hydroxylation with O2 and the second is oxidation of an NADH analogue with O2 to produce H2 O2 .
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University and SENTAN (Japan) Science and Technology Agency (JST), Suita, Osaka, 565-0871, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Hirose
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University and SENTAN (Japan) Science and Technology Agency (JST), Suita, Osaka, 565-0871, Japan. ookubo@chem.eng.osaka-u.ac.jp.|Division of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, 565-0871, Japan. ookubo@chem.eng.osaka-u.ac.jp.|Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 120-750, Korea. ookubo@chem.eng.osaka-u.ac.jp.
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 120-750, Korea. fukuzumi@chem.eng.osaka-u.ac.jp.|Faculty of Science and Technology, SENTAN (Japan) Science and Technology Agency (JST), Meijo University, Nagoya, Aichi, 468-8502, Japan. fukuzumi@chem.eng.osaka-u.ac.jp.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
mesh_terms: D000166:Acridines / Q000737:chemistry*; D001554:Benzene / Q000737:chemistry*; D002384:Catalysis; D004579:Electron Transport; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006900:Hydroxylation; D007501:Iron / Q000737:chemistry; D009243:NAD / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D011522:Protons
chemical_list: C480178:10-methyl-9,10-dihydroacridine; D000166:Acridines; D010636:Phenols; D011522:Protons; D009243:NAD; C028189:N-methylacridine; D006861:Hydrogen Peroxide; D007501:Iron; D001554:Benzene; D010100:Oxygen
keywords: hydroxylation; oxidation; oxygen; radical reactions; reaction mechanism