Hydrogen Peroxide In Aqueous Medium Research Articles

Controllable oxidation of sulfides to sulfoxides and sulfones with aqueous hydrogen peroxide in the presence of β-cyclodextrin

A facile procedure has been developed for the transition metal-free oxidation of sulfides to sulfoxides and sulfones and of sulfoxides to sulfones with hydrogen peroxide in aqueous medium in the presence of β-cyclodextrin as catalyst. The procedure allows formation of sulfoxide or sulfone to be controlled.

The Microenvironment Effect on the Generation of Reactive Oxygen Species by Pd−Bacteriopheophorbide

Generation of reactive oxygen species (ROS) is the hallmark of important biological processes and photodynamic therapy (PDT), where ROS production results from in situ illumination of certain dyes. Here we test the hypothesis that the yield, fate, and efficacy of the species evolved highly depend on the dye's environment. We show that Pd-bacteriopheophorbide (Pd-Bpheid), a useful reagent for vascular targeted PDT (VTP) of solid tumors, which has recently entered into phase II clinical trials under the code name WST09 (trade name TOOKAD), forms appreciable amounts of hydroxyl radicals, superoxide radicals, and probably hydrogen peroxide in aqueous medium but not in organic solvents where singlet oxygen almost exclusively forms. Evidence is provided by pico- and nanosecond time-resolved spectroscopies, ESR spectroscopy with spin-traps, time-resolved singlet oxygen phosphorescence, and chemical product analysis. The quantum yield for singlet oxygen formation falls from approximately 1 in organic solvents to approximately 0.5 in membrane-like systems (micelles or liposomes), where superoxide and hydroxyl radicals form at a minimal quantum yield of 0.1%. Analysis of photochemical products suggests that the formation of oxygen radicals involves both electron and proton transfer from (3)Pd-Bpheid at the membrane/water interface to a colliding oxygen molecule, consequently forming superoxide, then hydrogen peroxide, and finally hydroxyl radicals, with no need for metal catalysis. The ability of bacteriochlorophyll (Bchl) derivatives to form such radicals upon excitation at the near infrared (NIR) domain opens new avenues in PDT and research of redox regulation in animals and plants.

Tungstate‐Exchanged Mg‐Al‐LDH catalyst: An Eco‐Compatible Route for the Oxidation of Sulfides in Aqueous Medium.

The catalytic oxidation of sulfides selectively to sulfoxides and/or sulfones is realised for the first time with heterogeneous tungstate-exchanged Mg-Al-LDH catalyst using 30% hydrogen peroxide in aqueous media at a faster rate in quantitative yields at room temperature. The heterogeneous catalyst showed higher activity (TOF) over its homogeneous analogues and other heterogeneous catalysts reported so far. The catalyst is well characterised by various instrumental techniques such as FT-IR spectroscopy, thermal analysis (TGA and DTA), powder XRD and chemical analysis. The catalyst is reused for six cycles with consistent activity and selectivity.

Tungstate-exchanged Mg-Al-LDH catalyst: an eco-compatible route for the oxidation of sulfides in aqueous mediumIICT Communication No: 020222

The catalytic oxidation of sulfides selectively to sulfoxides and/or sulfones is realised for the first time with heterogeneous tungstate-exchanged Mg-Al-LDH catalyst using 30% hydrogen peroxide in aqueous media at a faster rate in quantitative yields at room temperature. The heterogeneous catalyst showed higher activity (TOF) over its homogeneous analogues and other heterogeneous catalysts reported so far. The catalyst is well characterised by various instrumental techniques such as FT-IR spectroscopy, thermal analysis (TGA and DTA), powder XRD and chemical analysis. The catalyst is reused for six cycles with consistent activity and selectivity.

Amperometric Enzyme Electrode for Hydrogen Peroxide Determination Prepared with Horseradish Peroxidase Immobilized in Polyvinylferrocenium (PVF + )

Steady state amperometric measurements of hydrogen peroxide in aqueous medium was performed by an enzyme electrode which was developed by electrostatic immobilization of the horseradish peroxidase, HRP, in poly(vinylferrocenium perchlorate), PVF+ClO, film. Amperometric measurements were performed at an applied potential of +0.7 V (vs. SCE). The effects of working temperature, enzyme concentration, film thickness and dissolved oxygen on the response of the electrode were elucidated. The responses of the PVF+E− electrode, PVF+ClO coated electrode and uncoated Pt electrode were compared. The activation energy and the apparent Michaelis-Menten constant were calculated for enzyme electrode system. The linear working range, the sensitivity and the stability of the biosensor were also determined. Mechanisms for the operation of the electrode with and without immobilizied enzyme in the polymer matrix are proposed.

CERIUM(IV) AMMONIUM NITRATE MEDIATED NITRATION OF COUMARINS

A new convenient method of nitration of coumarins using cerium(IV) ammonium nitrate (CAN) has been developed. Higher regioselectivity is observed with CAN and hydrogen peroxide in aqueous medium in comparison with CAN in acetic acid for nitration of 7-hydroxycoumarin, 7-hydroxy-4-methyl coumarin and their derivatives.

Oxidative cracking of precipitated hardwood lignin by hydrogen peroxide.

Precipitated hard-wood lignin (PHL) is a major byproduct in the biomass-to-ethanol process. Oxidative cracking of PHL by hydrogen peroxide in aqueous medium was investigated as a means to produce potentially useful chemicals. The cracking reaction takes place at moderate temperatures (80-160 degrees C), giving mono- and dicarboxylic acids as the main products. The yields of these products are in the range of 30-50% of initial lignin. The reaction mechanism and the product distribution are dependent upon the reaction conditions, especially the pH. The reaction under strong alkaline condition proceeds well even at low reaction temperatures (80-90 degrees C). Under acidic conditions, higher temperatures (130-160 degrees C) are required to attain the same degrees of cracking. The reaction patterns of the oxidative cracking reaction involve the cleavage of lignin ring, aryl ether bond, or other linkages within lignin. By using the findings of this investigation and those of previous work, we have illustrated the reaction pathways for degradation of PHL under alkaline and acidic conditions. Aldehydes and aromatic acids are intermediate products in the oxidative degradation of lignin. However, they were produced only in trace amounts owing to rapid degradation induced by hydrogen peroxide.

Kinetic investigations of azo dye oxidation in aqueous media

A detailed kinetic and spectroscopic investigation has been made of the oxidation of 4-(4-sulfophenylazo)-1-naphthol (Orange I, 4) and 1-(4-sulfophenylazo)-2-naphthol (Orange II, 5) and a series of specially synthesised, substituted 1-arylazo-2-naphthol dyes (6a, 6b) by hypochlorite, peracids and hydrogen peroxide in aqueous media. In all cases, observed second-order rate constants exhibit maxima in alkaline media at a pH equal to the midpoint of the pKA values of dye and oxidant. It is found that substituents upon the aryl ring ortho to the azo group suppress dye reactivity towards hypochlorite and, in addition, it is shown that peracids exhibit similar trends. In contrast, oxidation by hydrogen peroxide is enhanced by ortho substituents, suggesting that it functions via a different mechanism. Surprisingly, the dye common anion has been identified as the form of the dye most susceptible to oxidation by peracids and hypochlorite, with the undissociated oxidant molecules acting as electrophiles. In contrast, dye oxidation by hydrogen peroxide proceeds via the perhydroxyl anion and the hydrazone tautomeric form of the dye. The main function of ortho substituents is to increase the dye pKA, thereby influencing observed rates (k2obs) by changing the equilibrium concentration of reactive species. Substituents also exert an electronic effect on absolute rate constants, k2, giving good Hammett plots for both ortho and para substituents. Reactive oxygen species, e.g. singlet oxygen, superoxide or hydroxyl radicals, are not implicated in the rate-controlling step of the reaction.

Télomérisation en milieu aqueux, 2. Étude cinétique de la télomérisation de l'acide acrylique avec l'acide thioglycolique

AbstractThe telomerization of acrylic acid with thioglycolic acid initiated with hydrogen peroxide in aqueous medium is presented. In order to better control this reaction, the decomposition of H2O2 was first investigated by means of differential scanning calorimetry (DSC), leading to a very high value of the dissociation rate constant (kd), and then studied by volumetry in the presence of a mercaptan. This second method gave a higher value of kd (by about 6 orders of magnitude at 50°C). From the latter value, the ratio fkP2/kTe and the transfer constant of thiogiycolic acid, Ct, were determinated and compared with those reported in the literature. The kinetical parameters, obtained from theoretical and experimental values of DPn and the conversion of the monomer are in good agreement and allow to prepare telomers of acrylic acid with controlled chain length.

Decomposition behaviors of polymer peracid having thermo-responsive function prepared by photografting

Preparation of polymer peroxides with peracid type having thermo-responsive function was examined by using acrylic acid (AA)-grafted polyethylene film (thickness = 30 μm), into which thermo-responsive component, poly( N-isopropylacrylamide (NIPAAm)), was introduced by two photografting methods. One is photografting of AA/NIPAAm binary monomers and the other is two-step photografting, where AA is first photografted to the polyethylene film and then NIPAAm is introduced into the AA-grafted film by second-step photografting. The grafted film (one-step sample) prepared by the former method exhibited a higher thermo-responsive character than that (two-step sample) prepared by the latter method, where the grafted films swelled in water below and shrank above a lower critical solution temperature of poly(NIPAAm). The grafted films thus obtained were subjected to peroxidation with hydrogen peroxide in the presence of methanesulfonic acid. About 50% of the initial amount of peroxides on the AA-grafted sample disappeared after thermal decomposition at 25°C and 40°C for 60 min in aqueous medium. On the other hand, about 50% (25°C) and 90% (40°C) of peroxides on the one-step sample remained stable under the same conditions, resulting in an improved stability of the peroxides at higher temperature. However, the decomposition of the peroxides was markedly promoted by the irradiation with light of λ > 300 nm at 40°C. Almost all peroxides on the two-step sample disappeared while generating hydrogen peroxide in aqueous medium at 25°C and 40°C, showing a decomposition behavior different from those on the one-step sample.

Spectrophotometric determination of hydrogen peroxide in aqueous media with 1,2-di-(4-pyridyl)ethylene.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectrophotometric determination of hydrogen per-oxide in aqueous media with 1,2-di-4-pyridylethyleneThomas R. Hauser and M. A. KolarCite this: Anal. Chem. 1968, 40, 1, 231–232Publication Date (Print):January 1, 1968Publication History Published online1 May 2002Published inissue 1 January 1968https://doi.org/10.1021/ac60257a050RIGHTS & PERMISSIONSArticle Views123Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (239 KB) Get e-Alerts Get e-Alerts

Photo-induced reactions—IX : The hydroxylation of phenols by the photo-decomposition of hydrogen peroxide in aqueous media

The photolysis of hydrogen peroxide in the presence of phenols in aqueous solution was used for the hydroxylation of various phenols on a preparative scale. Irradiation with the light at 2537 Å resulted in the formation of ortho- and para-dihydroxy compounds as the main products. The ortho-hydroxylation is predominant. Dihydroxybenzenes were also hydroxylated. In the case of p-substituted phenols, only an ortho-hydroxylated derivative was obtained. p-Carboxy- and p-methoxy-phenols gave hydroquinone in addition to the usual catechol derivative. Photolysis under various conditions of p-cresol, gave the best yield of the catechol at pH 3–8. Irradiation of p-cresol in aqueous hydrogen peroxide with the light over 2800 Å at pH ca. 1, in the presence or the absence of uranyl sulphate, resulted in the formation of a mixture of dimers as the main products. The mechanisms, including hydrogen abstraction and addition of hydroxyl radicals, are discussed.

The hydroxylation of phenols by the photolysis of hydrogen peroxide in aqueous media

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