HbA/H2O2: an efficient biomimetic catalytic system for the oxidation of sulfides to sulfoxides

Human hemoglobin (HbA) catalyzed chemo-selective oxidation of sulfides to sulfoxides has been reported using hydrogen peroxide as an oxidant in a phosphate buffer. This biomimetic catalytic procedure was found to be simple, environmentally friendly, selective, and high yielding. Purified human oxyhemoglobin (HbA₀), crude human oxyhemoglobin, and ferryl oxyhemoglobin were used for sulfoxidation. HbA₀ and ferryl oxyhemoglobin (Fe⁺⁴O) efficiently catalyze the sulfoxidation reaction without over oxidation to the sulfone.     

Voltammetric method for the determination of H2O2 in rainwater

Summary Presented below is an electrochemical method for the determination of hydrogen peroxide levels in the atmospheric liquid water. The hydrogen peroxide concentration is determined by a voltammetric method involving a rotating disk electrode. The oxidation limiting current at +0.4 V/SCE is proportional to the concentration of hydrogen peroxide found in 1 mol/l KNO₃ containing a phosphate buffer, pH 7.5. An analytical blank is prepared in situ by addition of catalase enzyme to avoid interferences. The detection limit obtained is 5×10^–9 mol/l.     

Miniaturized and green method for determination of chemical oxygen demand using UV-induced oxidation with hydrogen peroxide and single drop microextraction

We report on a green method for the determination of low levels of chemical oxygen demand. It is based on the combination of (a) UV-induced oxidation with hydrogen peroxide, (b) headspace single-drop microextraction with in-drop precipitation, and (c) micro-turbidimetry. The generation of CO₂ after photolytic oxidation followed by its sequestration onto a microdrop of barium hydroxide gives rise to a precipitate of barium carbonate which is quantified by turbidimetry. UV-light induced oxidation was studied in the absence and presence of H₂O₂, ultrasound, and ferrous ion. Determinations of chemical oxygen demand were performed using potassium hydrogen phthalate as a model compound. The optimized method gives a calibration curve that is linear between 3.4 and 20 mg L^?1 oxygen. The detection limit was 1.2 mg L^?1 of oxygen, and the repeatability (as relative standard deviation) was around 5 %. The method was successfully applied to the determination of chemical oxygen demand in different natural waters and a synthetic wastewater.

Oxidation of sulfides to sulfoxides by optically active phosphite ozonides

A study was carried out on the oxidation of dialkyl and aryl alkyl sulfides by optically active phosphite ozonides in the case of the oxidation of methyl phenyl sulfide, methyl decyl sulfide, and benzyl octyl sulfide by the ozonides of L-(-)-menthyl o-phenylene phosphite, L-(-)-menthyl (2,2 -methylene-bis(4-methyl-6-tert-butylphenyl) phosphite, and L-(-)-bornyl (2,2 -methylene-bis(4-methyl-6-tert-butylphenyl) phosphite. These ozonides oxidize the indicated sulfides to the corresponding sulfoxides at –80°C. Partial asymmetric oxidation is possible. The addition of Ti(OC₃H₇-i)₄ increases the asymmetric control of the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2133–2135, September, 1990.     

Influence of the reaction conditions on the nature of the hydrogen peroxide oxidation products of furfural

UV irradiation causes no acceleration of the oxidation of furfural by hydrogen peroxide but maintains its occurrence at a uniform rate. Both with UV irradiation and without it, the oxidation of furfural by hydrogen peroxide takes place via the formation of intermediate peroxide compounds, with their subsequent conversion mainly into a mixture of -formylacrylic, maleic, and succinic acids. The ratio between the acids depends on the reaction conditions. The possibility has been shown of a directed oxidation to -formylacrylic acid.     

Pathways of photooxidation of 1,2,2,6,6-pentamethyl-4-piperidol by ketones

The photochemical oxidation of 1,2,2,6,6-pentamethyl-4-piperidol by ketones occurs exclusively at the methylamino group and, in the case of photolytically stable ketones, may lead to products of dimerization of the aminoalkyl radicals and recombination of the aminoalkyl and ketyl radicals and to a product of N-demethylation of the starting amino alcohol. When ketones that are unstable with respect to irradiation are used, photooxidation competes to a considerable extent with photodecomposition of such ketones. Spatial proximity of the aryl and -methyl groups are observed for the products of reductive addition of the ketones on the basis of the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1657–1661, December, 1982.     

Sulfur-containing carboxylic acids. 6. The syntheses of 3,3"-sulfinyldipropionic and 2,2"-sulfinyldiacetic acids

Pure sulfoxides of thiodialiphatic acids were obtained in high yields by oxidation of the corresponding sulfides in organic solvents. 3,3"-Sulfinyldipropionic acid was obtained by the reaction of hydrogen peroxide with thiodipropionic acid in acetone. 2,2"-Sulfinyldiacetic acid was synthesized by the reaction of thiodiglycolic acid with H₂O₂ in acetone containing acetic acid (26 mol. %). Pure 2,2"-sulfinyldiacetic acid was found to be stable in storage rather than labile as reported previously.     

Syntheses and structures of Osmium(II) and Osmium(VI) <Emphasis Type="Italic">meso</Emphasis>-tetra(benzo-15-crown-5)porphyrinates according to the spectral data

The reaction of meso-tetra(benzo-15-crown-5)porphyrin (H₂TCP) with the osmium carbonyl complex Os₃(CO)₁₂ yieds the corresponding osmium(II) porphyrinate OsTCP(CO). The oxidation of OsTCP(CO) with air oxygen and hydrogen peroxide in neutral and acidic media was studied. A preparative method for the synthesis of osmium(VI) meso-tetra(benzo-15-crown-5)porphyrinate (OsO₂) TCP by the oxidation of OsTCP(CO) with 50% hydrogen peroxide in acetic acid was developed. The structures of new osmium porphyrinates were determined by IR, ¹H NMR, and UV/Vis spectroscopies.     

Chemoselective sulfoxidation by H2O2 or HNO3 using a phosphate impregnated titania catalyst

A variety of organosulfur compounds have been selectively oxidized to the corresponding sulfoxides by either H₂O₂ or HNO₃ using a newly developed solid acid catalyst composed of 84.5% of TiO₂ and 15.5% of [Ti₄H₁₁(PO₄)₉]·nH₂O (n = 1-4). The chemoselective oxidation of sulfides in the presence of vulnerable groups such as -CN, -CC-, -CHO, or -OH, as well as sulfoxidation of substrates like benzothiazole, glycosyl sulfide, and dibenzothiophenes is some of the important attribute of the protocol. Nitric acid, under the present experimental conditions, brings about relatively better selectivity than hydrogen peroxide.     

VCl3‐Catalyzed Selective Oxidation of Sulfides to Sulfoxides Using H2O2 as Oxidant

VCl₃ is an effective catalyst for the catalytic oxidation of sulfides to afford sulfoxides in good yields using hydrogen peroxide as an oxidant.     

Fibre optic fluorometric enzyme sensors for hydrogen peroxide and lactate,based on horseradish peroxidase and lactate oxidase

An optical biosensor for the determination of hydrogen peroxide based on immobilized horseradish peroxidase is described. The fluorescence of the dimeric product of the enzyme catalysed oxidation of homovanillic acid is utilized to determine the concentration of H₂O₂. The membrane-bound enzyme is attached to a bifurcated fibre bundle permitting excitation and detection of the fluorescence by a fluorometer. The response of the sensor is linear from 1 to 130 M hydrogen peroxide; the coefficient of variation is 3%. The sensor is stable for more than 10 weeks. The operating pH for maximal sensor response is 8.15. This allows the sensor to be used in combination with oxidase reactions producing hydrogen peroxide, as is demonstrated with a co-immobilized lactate oxidase-horseradish peroxidase optode for the determination of L-lactate. The fluorescence intensity of this sensor depends linearly on the concentration of lactate between 3 and 200 M and a throughput of 10 samples per hour is possible. The precision is in the same range as that of the monoenzyme optode. The lifetime of the bienzyme sensor for lactate is considerably shorter than that of the peroxidase sensor; it is limited by the stability of the immobilized lactate oxidase enzyme. The sensor has been applied to the determination of lactate in control serum.     

Selective Hydrogenation of Diethyl Disulfide to Ethanethiol in the Presence of Sulfide Catalysts

The gas-phase reaction of diethyl disulfide hydrogenation at atmospheric pressure in the presence of supported transition metal sulfides was studied. The reaction of diethyl disulfide with hydrogen at T = 200°C resulted in ethanethiol, and the selectivity to ethanethiol was no lower than 94%. The selectivity decreased at a higher temperature because of diethyl disulfide decomposition to ethylene and hydrogen sulfide. The reaction of diethyl disulfide in the presence of hydrogen occurred at a higher rate and selectivity than that in an atmosphere of helium. The activity of metal sulfides supported on aluminum oxide was higher than on the other studied supports—aluminosilicate, silica gel, and a carbon support. Metal sulfides supported on Al₂O₃ were arranged in the following order according to their activity: Rh > Ru > Mo Pd > Ni > W. Bimetallic catalysts were less active than monometallic catalysts. The activity of catalysts increased with the sulfide sulfur content; the partial reduction of metal sulfides also increased the catalytic activity.     

Peroxidase-like activity of magnetoferritin

Magnetoferritin is a spherical biomacromolecule with a diameter of about 12 nm. It consists of a protein shell composed of apoferritin that is surrounding magnetic nanoparticles of magnetite (Fe₃O₄) or maghemite (γ-Fe₂O₃). Magnetoferritins with various iron content (loading factor) were synthetically prepared and their peroxidase-like activities studied via the oxidation of the chromogenic substrate N,N-diethyl-p-phenylenediamine sulfate by hydrogen peroxide to give a purple product with an absorption maximum at 551 nm. Magnetoferritin with higher loading factor exhibits a higher peroxidase-like activity. The catalytic activity was successfully applied to the determination of hydrogen peroxide in the 5.8 to 88.2 mM concentration range.

A glassy carbon electrode modified with FeS nanosheets as a highly sensitive amperometric sensor for hydrogen peroxide

Iron sulfides with different atomic ratios were synthesized by a hydrothermal method and used to modify a glassy carbon electrode. The various sulfides were compared to each other for their amperometric response to H₂O₂. It is found that FeS is the most adequate material. Operated in 0.1 M NaOH solution at 0.4 V (vs. Ag/AgCl), the sensor based on FeS displays a linear response that extends from 0.50 μM to 20.5 mM of H₂O₂, with a sensitivity of 36.4 μA mM^?1 cm^?2 and a detection limit of 0.15 μM (at an S/N ratio of 3). The sensor is selective, stable and reproducible.

Open image in new window

Graphical abstract Schematic of the synthesis of pomegranate flower-like FeS by a hydrothermal route using ferric chloride and thiourea (SC(NH₂)₂) as the precursors, and ethanolamine (EA) as the structure-guiding auxiliary agent. A glassy carbon electrode (GCE) modified with this material allows for amperometric sensing of hydrogen peroxide in 0.1 M NaOH solution with a 0.15 μM detection limit. 

     

Synthesis of 2,3-dihydroquinazolin-4(1<Emphasis Type="Italic">H</Emphasis>)-ones,disulfides and sulfoxides catalyzed by a zinc complex immobilized onto functionalized mesoporous MCM-41 as a mild and efficient catalyst

Zinc complex with 2-amino-3-hydroxy-pyridine ligand was immobilized onto chloropropyl-modified mesoporous silica MCM-41 (CP-MCM-41) via post-grafting method. The prepared catalyst has been characterized by low-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectrum, atomic adsorption spectroscopy and thermogravimetric analysis. The immobilized nano-structured material showed very good catalytic activity and excellent recycling efficiencies for the oxidation reaction of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides in the presence of aqueous hydrogen peroxide as oxidant at room temperature and the synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives in water.     

Nanoparticle supported,magnetically separable vanadium complex as catalyst for selective oxidation of sulfides

A magnetically recyclable vanadium(V) catalyst was synthesized by covalent anchoring of VO(salen)Cl on silica-coated Fe₃O₄ nanoparticles. This straightforward preparation yields magnetically separable Fe₃O₄@SiO₂@VO(salen) nanoparticles with high vanadium loading. These nanoparticles were efficient catalysts for selective oxidation of sulfides to corresponding sulfoxides with urea hydrogen peroxide in excellent yields. Leaching and recycling experiments revealed that the nanocatalyst can be applied for nearly complete oxidation of sulfides for at least five successive cycles.     

Polarographic Study of Reactions in the System 2-Furaldehyde-Hydrogen Peroxide-NaVO3

The oxidation of 2-furaldehyde to -formylacrylic acid in 0.1 N HClO₄ containing hydrogen peroxide and sodium vanadate was studied by polarography using a dropping mercury electrode. The conversion of 2-furaldehyde and the yield of the products were found to depend on the reactant ratio. A mechanism was proposed which includes preliminary complex formation between the reactants.     

Enantioselective oxidation of sulfides with hydrogen peroxide catalyzed by vanadium complex of sterically hindered chiral Schiff bases

Sterically hindered chiral Schiff base ligands 4a-d were prepared from an aldehyde derived from BINOL. The vanadium complexes of the ligands catalyze an efficient, enantioselective H₂O₂-promoted sulfoxidation of alkyl aryl sulfides, and enantioselectivities as high as 98-99% ee are observed in the sulfoxidation of benzyl aryl sulfides.     

Tantalum(V) or niobium(V) catalyzed oxidation of sulfides with 30% hydrogen peroxide

Tantalum(V) and niobium(V) are effective catalysts for the oxidation of sulfides with 30% hydrogen peroxide. The reaction of sulfides with 30% hydrogen peroxide catalyzed by tantalum(V) chloride or niobium(V) chloride in acetonitrile, i-propanol or t-butanol selectively provided the corresponding sulfoxides in high yields. The corresponding sulfones are efficiently obtained from the reaction of sulfides with 30% hydrogen peroxide in methanol catalyzed by tantalum(V) or niobium(V).