title: One-Step Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide Catalysed by Copper Complexes Incorporated into Mesoporous Silica-Alumina.
abstract: Benzene was hydroxylated with hydrogen peroxide (H2O2) in the presence of catalytic amounts of copper complexes in acetone to yield phenol at 298 K. At higher temperature, phenol was further hydroxylated with H2O2by catalysis of copper complexes to yieldp-benzoquinone. The kinetic study revealed that the rate was proportional to concentrations of benzene and H2O2, but to the square root of concentration of a copper(II) complex ([Cu(tmpa)]2+: tmpa = tris(2-pyridylmethyl)amine). The addition of a spin trapping reagent resulted in formation of a spin adduct of hydroperoxyl radical (HO2•), as observed by EPR spectroscopy, inhibiting phenol formation. HO2•produced by the reaction of [Cu(tmpa)]2+with H2O2acts as a chain carrier for the radical chain reactions for formation of phenol. When [Cu(tmpa)]2+was incorporated into mesoporous silica-alumina (Al-MCM-41) by a cation exchange reaction, the selectivity to production of phenol was much enhanced by prevention of hydroxylation of phenol, which was not adsorbed to Al-MCM-41. The high durability with turnover number of 4320 for the hydroxylation of benzene to phenol with H2O2was achieved using [Cu(tmpa)]2+incorporated into Al-MCM-41 as an efficient and selective catalyst.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology (JST), Suita, Osaka 565-0871, Japan.
authors.forename: Mihoko
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States.
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Karlin
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology (JST), Suita, Osaka 565-0871, Japan; Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea; Faculty of Science and Engineering, Meijo University, ALCA and SENTAN, Japan Science and Technology Agency (JST), Nagoya, Aichi 468-0073, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi