Catalysis of copper-containing transition metal hydrotalcite-like compounds in the phenol hydroxylation with hydrogen peroxide

Hydrotalcite-like compounds containing carbonate ion as the interlayer anion were prepared by coprecipitation under low supersaturation condition by mixing an aqueous solution of metal nitrates with an aqueous solutions of NaOH and Na2CO3, at room temperature, maintaining pH = 8-10 with vigorous stirring, Following the mixing, the resulting heavy slurry was aged at 353 K for 18 h with vigorous stirring, The precipitate was then filtered, washed several times with hot distilled water and dried in air at 353 K overnight, In this way, CuMI AlCO3-HTLcs and M-I AlCO3-HTLcs were synthesized and characterized by means of XRD and IR, The catalysis of the above mentioned HTLcs were investigated in the phenol hydroxylation with H2O2. The results indicated that all of the copper-containing HTLcs had a higher catalytic activity in the reaction, However, those catalysts that did not contain copper had no catalytic activity in this reaction, This means that copper was the active center in the phenol hydroxylation. Meanwhile, the mechanism was also proposed, which could be used to explain the main reason for higher activity for CuCuAlCO3-HTLcs in the phenol hydroxylation and the effect of Mg2+, Zn2+, Co2+, Ni2+ on activity of CuMI AlCO3-HTLcs.

Chemical polymerization of aniline with hydrogen peroxide as oxidant

Oxidative polymerization of aniline in the presence of H2O2/Fe2+/HCl was carried out, and polyaniline obtained showed similar molecular structure compared to that prepared in (NH4)(2)S2O8 system.

Mass spectrometric evidence for the generation of benzyne from benzoyl peroxide in thermolysis

Benzoyl peroxide gave rise to benzoic acid (at m/z 122) in its electron impact mass spectrum, and its perdeuterated counterpart produced perdeuterobenzoic acid, C6D5CO2D, at m/z 128 under the same conditions, An intramolecular hydrogen abstraction is proposed for the formation of benzoic acid from the peroxide in thermolysis. As a result of this reaction, benzyne would be generated simultaneously. Anthracene was employed to trap any of the reactive intermediate benzyne. Collision-induced dissociation of the ion of m/z 254 from the mixture of benzoyl peroxide and anthracene indicated that triptycene was obtained by the trapping reaction, therefore confirming that benzyne is generated from benzoyl peroxide in thermolysis.

Direct electrochemical identification of an activated intermediate formed by cytochrome C with hydrogen peroxide

An activated intermediate formed from H2O2 and cytochrome C is identified by direct electrochemical measurements.

KINETIC-STUDY OF ELECTROCATALYTIC REDUCTION OF HYDROGEN-PEROXIDE AT IRON(III) PORPHYRIN MODIFIED GLASSY-CARBON ELECTRODE IN ALKALINE-MEDIUM USING THE ROTATION-SCAN METHOD

Reduction of hydrogen peroxide at a glassy carbon (GC) electrode modified with sigma-bonded pyrrole iron(III) octaethylporphyrin complex, (OEP)Fe(Pyr), was studied by cyclic voltammetry and a rotating disk electrode. In 0.1N NaOH solution, it is shown that such an (OEP)Fe(Pyr)/GC electrode has a significant catalytic activity towards hydrogen peroxide reduction (E(D) = -0.80 V, k = 0.066 cm s(-1)); however, the electrode stability is low. The deactivation is observed when the reaction charge (Q) is passing through the (OEP)Fe(Pyr)/GC disk electrode. A linear rotation scan method is applied to study the kinetic process by determining the disk electrochemical response (i(D)) to rotation rate (omega) at a definite disk potential (E(D)). Considering that the number of adsorbed electroreduced catalyst molecules (Red) varies according to the disk potential, a factor theta(= Gamma(Red)/(Gamma(Red) + Gamma(Ox))) is introduced to describe the electrode surface area fraction for electroreduced species. The obtained Koutecky-Levich equation is applicable whatever the potential is.

MEDIATORLESS HYDROGEN-PEROXIDE ELECTRODE BASED ON HORSERADISH-PEROXIDASE ENTRAPPED IN POLY(O-PHENYLENEDIAMINE)

A mediatorless H2O2 sensor based on coelectropolymerization of horse radish peroxidase (HRP) and o-phenylenediamine (o-PD) is described. The electrode responds to H2O2 in a few seconds and gives a current density of 73.3 nA 1 mu mol(-1) cm(-2) at -100 mV

CHEMICAL-IONIZATION MASS-SPECTROMETRY OF BENZOYL PEROXIDE - A RADICAL AROMATIC-SUBSTITUTION RESULTING IN BIPHENYLCARBOXYLIC ACID IN THE GAS-PHASE

A radical aromatic substitution resulting in biphenylcarboxylic acid is inferred for the decomposition of benzoyl peroxide from the chemical ionization and collision-induced dissociation mass spectra. The thermolysis of benzoyl peroxide gives rise to a benzoyloxy radical, which undergoes rapid decarboxylation and hydrogen abstraction leading to phenyl radical and benzoic acid, respectively. Attack of the resulting phenyl radical on the benzoic acid results in bipbenylcarboxylic acid. On the other hand, the phenyl radical abstracts a hydrogen atom to yield benzene, which is then subjected to the attack of a benzoyloxy radical, affording phenyl benzoate. This substitution reaction rather than the recombination of benzoyloxy and phenyl radicals is found to be responsible for the formation of phenyl benzoate under the present conditions.

Electrochemical measurement of hydrogen peroxide in plasma: Evaluation of freshwater prawn (Macrobrachium rosenbergii) and crucian carp (Cyprinus carpio) phagocytes under natural conditions

An electrochemical technique for the real-time detection of hydrogen peroxide (H2O2) was employed to describe respiratory burst activity (RBA) of phagocytes in plasma which can be used to evaluate the ability of immune system and disease resistance. The method is based upon the electric current changes, by redox reaction on platinum electrode of extracellular hydrogen peroxide (H2O2) released from phagocytes stimulated by the zymosan at 680 mV direct current (d.c.). Compared with the control, activation of respiratory burst by zymosan particles results in a high amperometric response, and a current peak was obtained during the whole monitoring process. The peak current was proved by addition Of Cu2+ and other controls, to be the result of intense release of H2O2 from phagocytes. The peak area was calculated and used to evaluate the quantity of effective H2O2, which represents the quantity of H2O2 beyond the clearance of related enzymes in plasma. According to Faraday's law, the phagocytes' ability of prawns to generate effective H2O2 was evaluated from 1.253 x 10(-14) mol/cell to 6.146 x 10(-14) mol/cell, and carp from 1.689 x 10(-15) Mol/Cell to 7.873 x 10(-1)5 mol/cell. This method is an acute and quick detection of extracellular effective H2O2 in plasma and reflects the capacity of phagocytes under natural conditions, which could be applied for selecting species and parents with high immunity for breeding in aquaculture. (c) 2007 Elsevier Ltd. All rights reserved.

Reaction-controlled phase transfer catalysis for styrene epoxidation to styrene oxide with aqueous hydrogen peroxide

The epoxidation of styrene catalyzed by a reaction-controlled phase transfer catalyst [(C18H37(30%)+C16H33(70%))N(CH3)(3))(3)](3)-[PW4O16] with H2O2 in a biphasic medium was investigated. Under certain conditions, the selectivity for styrene oxide was 95%, the conversion of styrene based on H2O2 was 85%, and the reaction time was less than 1 h. During the reaction, this catalyst powder formed soluble active species by the action of H2O2, was recovered as a precipitate, and was reused after H2O2 was used up. After two times recycling, the catalyst kept almost the same activity.