Aromatic hydroxylation by fenton reagents {Reactive intermediate[Lx+FeIIIOOH(BH+)], not free hydroxyl radical (HO·)}

DFT Study of the Active Intermediate in the Fenton Reaction

“…It has been proposed that the hydroxylation of an aromatic substrate by Fenton reagents, such as the hydroxylation of benzene to phenol, does not occur through a free hydroxyl radical mechanism but rather through a reactive intermediate [L x Fe II (OOH À )(BH )] 2 (X) obtained by nucleophilic addition of HOOH to the iron center, where L x bpy (bipyridine), or OPPh 3 (triphenylphosphine oxide) and B py (pyridine), or H 2 O. [7,9] The formation of the active species X implies that after the nucleophilic addition of HOOH the first step is a proton transfer from the hydrogen peroxide to one ligand (or to the solvent) and not the OÀO bond breaking. In this section we explore the possible stability of such an intermediate in the case of a ferrous complex with water Figure 3 and Table 2), we see that the hydrogen H18 points toward the oxygen O4 of the nearest water ligand.…”

“…Wink et al [8] observed an intermediate in the oxidation of Nnitrosodimethylamine by the Fenton reagent in acidic aqueous solution which they identified with a peroxo species Fe II OOH. Sawyer et al [7,9] have also suggested the formation of a hydroperoxo complex by comparing relative reactivities of . OH and Fenton oxidants with several hydrocarbon substrates in nonaqueous medium.…”

“…The alternative intermediate [Fe II (H 2 O) 4 (OOH À )(H 3 O )] 2 suggested in the literature [7,9] has been found to be unstable against the primary intermediate. The reaction path observed from 1 to 3 supports a picture of the Fenton reaction in which free hydroxyl radicals do not play a crucial role, and suggests a high-valent Fe IV oxo complex as the most stable intermediate.…”

Roles of Copper and a Conserved Aspartic Acid in the Autocatalytic Hydroxylation of a Specific Tryptophan Residue during Cysteine Tryptophylquinone Biogenesis

“…As with traditional iron Fenton chemistry, the copper Fenton-like chemistry generates reactive hydroxyl radicals and the Cu(I)/Cu(II) reaction is known to generate nonspecific aromatic hydroxylation 39, 40 . The LodA precursor contains one or more coppers in either a Cu(I) state, or Cu(II) state that could be reduced via Cys516, prior to CTQ formation.…”

Insights into the Aryl–Aryl Exchange between Palladium and Phosphane Ligands in Pd II Complexes: Preparation of Phthalocyanine‐Containing Phosphonium Salts

“…In the last few years many scientists, ourselves included, have concentrated on the preparation of unsymmetrically functionalized phthalocyanines [2,3] and binuclear Pc derivatives in which the macrocyclic units are fused to each other [4,5] or bridged through different kinds of spacers. [6±8] Our interest in noncentrosymmetric and octupolar [9] systems for nonlinear optical (NLO) applications [10] as well as in the preparation of molecular materials with multiple functions led us to the synthesis of phosphonium salts containing one phthalocyanine unit ( Figure 1). Pc-containing phosphonium cations are targets of choice for the preparation of hybrid materials that combine magnetism with NLO properties.…”