Oxidation of polycyclic aromatic hydrocarbons by an oxoferryl porphyrin π-cation radical

Copper(i)-based oxidation of polycyclic aromatic hydrocarbons and product elucidation using vacuum ultraviolet spectroscopy and theoretical spectral calculations

Fluorinated 1,3,5-triazapentadienyl complexes of copper catalyze the oxidation PAHs to quinones using H₂O₂as an oxidant under mild conditions.

Effects of metal and porphyrin structure on the yield and chemoselectivity of naphthalene oxidation: a comparative study for manganese and iron

Oxidation of naphthalene was performed with various manganese and iron porphyrins as catalysts and metachloroperbenzoic acid, tert-butylhydroperoxide, and hydrogenperoxide as oxidants, in the presence of imidazole as cocatalyst. With m-CPBA, in low concentration of catalyst, iron porphyrin shows a higher catalytic activity than manganese porphyrin, while a greater amount of manganese porphyrin is needed for having a good catalyst. In the presence of excess amount of H 2 O 2 oxidant in CH 3 OH solvent, manganese porphyrin acts better than iron porphyrin; however with the same oxidant and in aprotic solvent such as CH 3 CN : CH 2 Cl 2 again iron shows a higher activity than manganese. Moreover, the effects of metalloporphyrin concentration on the selectivity, activity and stability of catalyst were studied in H 2 O 2-catalytic oxidation.

Effects of pH and organic co-solvents on the oxidation of naphthalene with peroxosulfate catalyzed by iron(III) tetrakis(p-sulfonatophenyl)porphyrin

The oxidation of naphthalene was investigated in a biomimetic catalytic system using KHSO 5 and iron(III) tetrakis(p-sulfonatophenyl)porphyrin ( FeTPPS ) in order to elucidate the influence of solution forms, such as buffer pH and co-solvent types, on the reaction. 1,4-naphthoquinone was the main byproduct and the efficiency of oxidation, particularly 1,4-naphthoquinone formation, was influenced by pH and the type of co-solvent used. The most efficient conversion of 1,4-naphthoquinone was observed at an acidic pH (= 3). At higher pH , the formation of μ-oxo species ( OFe 2( TPPS )2) leads to a decrease of the percentage of naphthalene oxidized. In addition, the organic co-solvents (methanol, ethanol, 2-propanol and acetonitrile) influenced the amounts of naphthalene conversion. The amounts of 1,4-naphthoquinone formed were related to the electron donating character of the organic co-solvents.

Biomimetic chemistry as a useful tool for studying reactive metabolites of pesticides

Most organophosphate (OP) pesticides require metabolic activation before attacking the target site, as opposed to chemical nerve agents, such as VX and sarin, which inhibit the enzyme directly. The majority of OP pesticides exhibit weak anticholinesterase activity in vitro compared to their In Vivo activity. Biooxidation is probably the principal route by which these pesticides are activated or detoxified. The oxidized product, usually a short-lived intermediate, may either hit the target directly or hydrolyze rapidly or, following a rearrangement reaction, convert to another species with enhanced reactivity (metaphosphate) or lose its phosphorylation or carbamoylation properties. Biomimetic studies of these processes, using various model systems, have important advantages: in some cases they allow for identifying short-lived intermediates, formed metabolically, and direct monitoring of the systems' properties by NMR. Once identified, they may be synthesized in large amount to investigate their adverse effects, if any. Biomimetic studies allow for monitoring reactions at low temperature seeking transient intermediates and evaluation of activation and detoxification mechanisms as well as mode of action based on chiral isomers. This, in turn, allows for determination of whether certain compounds act directly, on preactivation, or both, and the possible design of safer pesticides. This paper covers over three decades of extensive fundamental and applied research that has been carried out at the Environmental Chemistry and Toxicology Laboratory (ECTL) at the University of California at Berkeley under the supervision of Prof. John E. Casida.

Photochemically-induced radical reactions of zinc phthalocyanine

Direct measurements of the radical reaction products following the electrochemical and photochemical oxidation and reduction of a metallophthalocyanine pi-ring are reported. Electrospray mass spectrometry was used to detect the presence of the anion zinc(II) (1,4,8,11,15,18,22,25-octafluoro, 2,3,9,10,16,17,23,24-octaperfluoroisopropylphthalocyanine chloride, [ZnperF(64)Pc(-2) (Cl)](-), and its pi ring anion radical species, [ZnperF(64)Pc(-3)(Cl)](2-). This paper describes the use of ESI-MS techniques to determine the products of an on-line, photochemical radical oxidation, using CBr(4) as a sacrificial photoinduced oxidizing agent, which oxidized the radical, [ZnperF(64)Pc(-3)(Cl)](2-) species to [ZnperF(64)Pc(-2)(Cl)](-), where the complete reaction was detected directly by the mass spectrometer. This study makes use of electrospray mass spectrometry to detect the presence of an anion radical as the key component in the ring-reduced species and to monitor the immediate products of the important class of photochemical reduction and oxidation reactions in which radicals of the Zn Pc are formed in situ.

Radical mediated indirect oxidation of a PEG-coupled polycyclic aromatic hydrocarbon (PAH) model compound by fungal laccase

A high molecular model compound of polycyclic aromatic hydrocarbon was synthesised by coupling pyrene to PEG(5000). The pyrene-PEG was used for the study of a laccase-mediator-system. To prevent direct contact between the substrate and the enzyme the two were kept in their own compartments separated by a membrane. The low molecular mediators, 1-hydroxybenzotriazole and 2, 2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid), which were oxidised by laccase to the corresponding radicals or cations permeated the membrane and reacted with the pyrene-PEG model compound. Oxidation of the model compound resulted in an alpha-oxidation of the alkyl-chain leading to two main oxidation products. The same oxidation products were obtained in the reaction system without a membrane.