Oxidation Of Various Organic Substrates Research Articles

Synthesis of quercetin functionalized chitosan and determination of antioxidant properties

This paper is dedicated to the synthesis of a copolymer with reducing properties obtained by functionalizing chitosan with quercetin and determining the antioxidant activity of the derivatives obtained depending on the molar mass of the polymer. For this purpose, low molecular weight chitosan was obtained by oxidizing commercial chitosan with hydrogen peroxide and further functionalization with quercetin by the covalent grafting method. The functionalization process was performed through the following steps: functionalization of chitosan with ethyl chloroformate to increase the reactivity of the amine group to the hydroxyl group of quercetin and grafting the quercetin molecule to the synthesized intermediate. The comparative antioxidant properties of the composite obtained by grafting technical chitosan with quercetin and by grafting low molecular weight chitosan were studied by the DPPH (2,2-diphenyl-1-picrylhydrazyl radical) method. The obtained results indicate that a decrease in the molecular weight of chitosan contributed to its grafting with quercetin. As a result, the functionalized polymer composite acquired a higher antioxidant activity and can be successfully used to inhibit the oxidation of various organic substrates in the cosmetic, food and pharmaceutical industries.

Tungsten Peroxopolyoxo Complexes as Advanced Catalysts for the Oxidation of Organic Compounds with Hydrogen Peroxide

Selective oxidation of organic substrates by environment-friendly oxidizing agents is an important ingredient of the sustainable chemical industry. Here we report a comprehensive study in the field of metal peoroxocomplex catalysis for the selective liquid phase oxidation of various organic substrates. A number of well-defined bi-functional tungsten complex catalysts with tetra nuclear structure {PO4[WO(O2)2]4}3- in combination with a phase-transfer agents were synthesized. The structural properties were thoroughly studied using of IR, Raman and EXAFS spectroscopy. By combining different spectroscopy techniques were able to elucidate the effect of quaternary ammonium cations on the structural properties of the resulting peroxo complexes. The catalytic properties of these well-defined material were then evaluated in bi-phasic selective oxidation of cyclooctene, methyl oleate and N-phosphonomethyliminodiacetic acid with hydrogen peroxide under mild conditions. For every substrate we were able to achieve high conversion at the selectivity towards a target product close to 100%.

Guaiakol Peroksidazın Soğan Köklerinden Afinite Kromatografisi ile Saflaştırılması

Peroksidazlar, hidrojen peroksit varlığında çeşitli organik substratların oksidasyonunu katalizleyen ve yapılarında hem grubu bulunduran enzimlerdir. Özellikle bitki peroksidazları, endüstride, klinik tanıda, biyosensör yapımında ve organik sentez reaksiyonlarında sıklıkla kullanılır. Ticari değerleri nedeniyle bu enzimlerin farklı kaynaklarda tanımlanması ve saflaştırılması büyük öneme sahiptir. Bu çalışmada peroksidaz enzimi ilk kez aminobenzohydrazide tabanlı afinite kromatografi tekniği kullanılarak soğan köklerinden 37.7 verimle 750 kat saflaştırıldı. Saflaştırılan enzimin moleküler ağırlığını belirlemek için SDS-PAGE yapıldı ve 51.2 kDa’da tek bant gözlendi. Ayrıca enzimin guaiakol, ABTS ve pirogallol substratları için KM değerleri sırasıyla 3.44, 0.46 ve 21.27 mM olarak olarak hesaplandı.

Iron-Decorated, Guanidine Functionalized Metal-Organic Framework as a Non-heme Iron-Based Enzyme Mimic System for Catalytic Oxidation of Organic Substrates

A novel porous functionalized metal-organic framework (MOF) as a non-heme iron-based enzyme mimic system was achieved via two-step post-synthetic modification of the MIL-101(Cr)-NH2, and characterized by FT-IR, PXRD, TGA, SEM, EDS, CHN, BET surface area, and ICP-OES analyses. This new modified MOF (MIL-101(Cr)-guanidine-Fe) has been demonstrated to be a highly efficient, active, and reusable catalyst for oxidation of various organic substrates, including alcohols, alkenes and alkyl arenes at room temperature using H2O2 as an oxidant.

Catalyzed Oxidation of Carotenoids by Lactoperoxidase in the Presence of Ethanol.

The discovery of the lactoperoxidase system as a biocatalyst in milk was a landmark finding. The activation of this system using hydrogen peroxide (H2O2) raised hopes for oxidation of various organic substrates. The involvement of lactoperoxidase system in the catalyzed-oxidation of carotenoids in the whey proteins, and the effect of various solvents on carotenoids' oxidation reaction rate has been studied. However, there is no evidence for this reaction without the addition of oxidizing agents, such as peroxides. Here, we reveal that carotenoids are oxidized through the addition of just ethanol in the presence of lactoperoxidase. The oxidation of carotenoids through this exquisite strategy is ∼360 times faster than harnessing the lactoperoxidase system in whey proteins via the addition of hydrogen peroxide. Bearing in mind that ethanol is not an oxidizing agent, this observation suggests a potential paradigm shift in our understanding of lactoperoxidase and catalyzed oxidation in biochemical systems.

Catalytic activity of an iron(III) Schiff base complex bound in a polymer resin

An iron(III)–ferrocene complex and its heterogeneous analogue bound in a polymer resin have been prepared and employed as catalysts for the oxidation of various organic substrates. Characterization of the heterogeneous and homogeneous complexes was done by SEM, EDAX, TGA, FT-IR, DRS-UV, and spectroscopy. The catalyst’s activity, stability, and reusability were investigated through industrially relevant oxidation reactions. The solid iron(III)–ferrocene Schiff base complex gave more effective results than the solid-supported ferrocene Schiff base ligand. The antimicrobial activities of the molecular complex and free ligand were studied for Gram-positive and Gram-negative bacteria.

Oxidation of organic compounds by hydrogen peroxide using polymer-anchored azo-metal catalysts

Polymer-anchored azo complexes of Cu(II) and Ni(II) were synthesized by the reaction of chloromethylated polystyrene, 3-aminophenol, and 1-nitroso-2-naphthol with the metal chlorides. The catalytic activities of these complexes were studied in the oxidation of various organic substrates including alkenes, alcohols, alkanes, and sulfides with 30 % aqueous hydrogen peroxide. The structures of both catalysts have been investigated by physiochemical methods. Both catalysts proved to be very stable and could be reused more than five times without significant loss of activity. Furthermore, these catalysts require very mild reaction conditions.

Catalytic activity of a reusable polymer‐anchored nickel(II)–phenanthroline complex on the oxidation of various organic substrates

AbstractA polymer‐anchored nickel(II)–phenanthroline complex [polyNi(II)–phen] was synthesized and used effectively as a reusable catalyst in various oxidation reactions in the presence of tert‐butylhydroperoxide as an oxidant in acetonitrile medium. The catalyst was characterized with elemental analysis, atomic absorption spectrometry (AAS), thermogravimetric analysis, scanning electron microscopy, and spectrometric methods such as diffuse reflectance spectroscopy, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. The study of the effects of the time, temperature, oxidant, catalyst concentration, molar ratio of substrate to oxidant, and solvent in the oxidation of styrene individually gave the optimized reaction conditions. Under optimized conditions, the catalyst exhibited good conversions for the oxidation reactions of various olefins, alkanes, aromatic alcohols, and thioethers. The catalyst was easily recovered by simple filtration and reused for more than five times with consistent catalytic activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis, characterization, and catalytic activity of a polymer-supported copper(II) complex with a thiosemicarbazone ligand

A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates including alkenes and alcohols using H2O2 as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out.

Alteration of the physicochemical properties of catalysts based on aqueous solutions of Mo-V-P heteropoly acids in redox processes

Selective catalytic oxidation of various organic substrates with O2 in the presence of aqueous solutions of Mo-V-P heteropoly acids (HPA) is carried out via two stages in separate reactors. In stage (1), a substrate is oxidized into a desired product while HPA is reduced. The reduced form of HPA is oxidized with O2 in stage (2). A set of the physicochemical properties of the homogeneous catalyst has been found to alter continuously during these redox processes. Using a solution of the modified high-vanadium HPA (H12P3Mo18V7O85), we demonstrate that the density, viscosity, and pH of this solution reach their maxima after reaction (1) and attain their minima after reaction (2). On the contrary, the redox potential of the solution is minimum after reaction (1), and maximum after reaction (2). All alterations of the physicochemical properties of the catalyst are found to be completely reversible.

Synthesis, Crystallization Mechanism, and Catalytic Properties of Titanium-Rich TS-1 Free of Extraframework Titanium Species

A new route to the synthesis of TS-1 has been developed using (NH4)2CO3 as a crystallization-mediating agent. In this way, the framework Ti content can be significantly increased without forming extraframework Ti species. The prepared catalyst had a Si/Ti ratio as low as 34 in contrast to the ratio of 58 achieved with the methods A and B established by the Enichem group (Clerici, M. G.; Bellussi, G.; Romano, U. J. Catal. 1991, 129, 159) and Thangaraj and Sivasanker (Thangaraj, A.; Sivasanker, S. J. Chem. Soc., Chem. Commun. 1992, 123), respectively. The material contained less defect sites than the samples synthesized by the other two methods. As a result, it showed much higher activity for the oxidation of various organic substrates, such as linear alkanes/alkenes and alcohols, styrene, and benzene. The crystallization mechanism of TS-1 in the presence of (NH4)2CO3 was studied by following the whole crystallization process with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetry/differential thermal analysis (TG/DTA), inductively coupled plasma atomic emission spectrometry (ICP), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-vis spectroscopy, and (29)Si MAS (magic-angle spinning) NMR spectroscopy techniques. It was shown that the presence of (NH4)2CO3 not only drastically lowered down pH, slowing down the crystallization process and making the incorporation of Ti into the framework match well with nucleation and crystal growth, but also modified the crystallization mechanism. It seems that the solid-phase transformation mechanism predominated in the crystallization process initiated by dissociation, reorganization, and recoalescence of the solidified gel although a small amount of nongelatinated Ti shifted to the solid during the crystal growth period. In contrast, a typical homogeneous nucleation mechanism occurred in the method A system. Thus, although in the method A system most of Ti cations was inserted into the lattice after the crystallization was nearly completed, the inclusion of Ti started at the earlier nucleation period in the presence of (NH4)2CO3. This is favorable for the incorporation of Ti into the framework, resulting in a more homogeneous distribution of Ti in the framework. Oxidation of 1-hexene and 2-hexanol over the samples collected during the whole crystallization process indicated that condensation of Ti-OH and Si-OH proceeded even after the crystallization was completed. This resulted in an increase in hydrophobicity and an overall improvement in microscopic character of Ti species and consequently a great increase in the catalytic activity with further progress of crystallization.

Novel Michael Addition Products of Bis(amino acidato)metal(II) Complexes: Synthesis, Characterization, Dye Degradation, and Oxidation Properties

Michael addition reactions of bis(amino acidato)metal(II) complexes (metal = copper, nickel, zinc; amino acid = glycine, dl-alanine, l-alanine) with acrylonitrile have been carried out under various experimental conditions in the absence of a base, resulting in mono- and disubstituted products in high yield, including partially hydrolyzed products. A reaction mechanism for the Michael addition on the nitrogen atom of the coordinated amino acid moiety, replacing the amino hydrogen atom(s), is proposed. All of the products have been characterized by Fourier transform infrared spectroscopy, electron paramagnetic resonance spectra, and elemental and electrochemical analyses. The single-crystal structures of bis( N-cyanoethylglycinato)copper(II) monohydrate ( 1a), diaquabis( N-cyanoethylglycinato)nickel(II), aquabis( N, N-dicyanoethylglycinato)copper(II) ( 2a), and bis[( N-propionamido- N-cyanoethyl)glycinato]copper(II) dihydrate ( 4a) have been confirmed by X-ray diffraction techniques. The products 1a, 2a, 4a, and bis( N-propionamidoglycinato)copper(II) monohydrate ( 3a) have been used as catalysts for the degradation of a phenol red dye and mild oxidation of various organic substrates in the presence of hydrogen peroxide. The monosubstituted complexes have been found to catalyze the reactions to a greater extent than the disubstituted complexes.

Oxovanadium(IV) complex of β-alanine derived ligand immobilised on polystyrene for the oxidation of various organic substrates

Abstract Tridentate Schiff base (H2fsal-β-ala) obtained from 3-formylsalicylic acid and β-alanine has been covalently bonded to divinylbenzene cross-linked chloromethylated polystyrene. This chelating resin, abbreviated as PS-H2fsal-β-ala (PS = polymeric support), reacts with vanadyl sulfate in DMF to give polymer bound complex, PS-[VO(fsal-β-ala) · DMF], formation of which has been confirmed by various physiochemical methods such as elemental analysis, FT-IR and diffused reflectance spectra, thermo gravimetric analysis, and scanning electron micrograph. Catalytic potential of PS-[VO(fsal-β-ala) · DMF] has been tested for the oxidation of various organic substrates such as benzene, cumene, naphthalene, cyclohexane, styrene, cyclohexene and trans-stilbene in the presence of 30% H2O2 as an oxidant. Oxidation products obtained from each substrate have been characterised by gas chromatography and their identities confirmed by gas chromatography–mass spectrometry.

4-Benzylpyridinium Fluorochromate: An Efficient and Selective Oxidant for Organic Substrates

A new chromium(VI) reagent, 4-benzylpyridinium fluorochromate, was prepared and used for oxidation of various organic substrates under solvent-free conditions. The reagent selectively converts primary benzylic alcohols to their corresponding carbonyl compounds in the presence of primary aliphatic alcohols.

Tris(3,5-dimethylpyrazole)copper(II) nitrate: as an oxidation catalyst

Tris(3,5-dimethylpyrazole)copper(II) nitrate ( A) is a catalyst for mild oxidation of various organic substrates. It acts as catalyst for conversion of benzylamine to benzaldehyde in the presence of hydrogen peroxide. Various benzylic alcohols are converted to corresponding aldehydes and acids by the catalytic amount of the complex ( A) with hydrogen peroxide at room temperature. The complex also catalyses dimerisation of 2,6-dimethylphenol and thiophenol. The thermal decomposition of tris(3,5-dimethylpyrazole)copper(II) nitrate at 500 °C gives CuO having the monoclinic crystal system. The cyclic voltammogram of the complex tris-(3,5-dimethylpyrazole)copper(II) nitrate shows a quasi-reversible redox cycle at −101 mV ( E 1/2) versus the Ag/AgCl electrode (+ve scan; scan speed 100 mV/s). The Δ E between anodic and cathodic peaks is 110 mV ( i pa/ i pc = 1.2).

Triphase, solvent-free catalysis over the TS-1/H 2O 2 system in selective oxidation reactions

Solvent-free, triphase conditions (solid-liquid-liquid) used in the oxidation of various organic substrates over the TS-1/H 2O 2 system (vis-à-vis conventionally used biphase conditions in the presence of a co-solvent) exhibit: (i) significant enhancement (3–10 times) in the reaction rates in the hydroxylation of aromatics (such as benzene, toluene, anisole and benzyl chloride), along with a reversal in regioselectivity of the products of substituted benzenes; and (ii) Baeyer-Villiger (BV) oxidation/rearrangement of cyclohexanone and acetophenone. In the case of benzyl chloride, triphase conditions resulted in the ring hydroxylation forming p-hydroxy and o-hydroxy benzyl chloride (75%) ( para:ortho ratio 85:15) along with side-chain oxyfunctionalization followed by HCl removal directly forming benzaldehyde (no formation of benzyl alcohol through hydrolysis). During BV oxidation, cyclohexanone and acetophenone gave caprolactone and phenyl acetate, respectively, as major products (70–90% selectivity). The other reaction was ring oxidation (30-10%) to hydroxy cyclohexanone and corresponding diketones (cyclohexanone) or hydroxy-acetophenones (acetophenone). Addition of a catalytic amount of mineral acid (H 2SO 4) significantly increased the conversion. Such reaction routes do not occur at all in the presence of co-solvent under biphase conditions. Factors responsible for enhancement in activity, change in regioselectivity and new routes are: (i) relative hydrophobic nature and restricted pore dimensions of titanium silicates; (ii) competitive diffusion of substrate with co-solvent; and (iii) Brönsted acidity of titanium silicates in the presence of H 2O 2 and water. Thus the present study opens up a new area where titanium silicate will be quite useful in various organic transformations, in an eco-safer way.

Studies on transition-metal oxo and nitrido complexes. 13. Perruthenate and ruthenate anions as catalytic organic oxidants

Oxo complexes of ruthenium are effective catalysts for the selective oxidation of various organic substrates. Thus the ruthenate ion trans-[Ru(OH)[sub 2]O[sub 3]][sup 2[minus]], which is stable above pH 12 in aqueous base, with persulfate as cooxidant will oxidize primary alcohols to carboxylic acids and secondary alcohols to ketones, the perruthenate ion [RuO[sub 4]][sup [minus]], which is stable from pH 8 to 12 in aqueous base, will also effect such oxidations stoichiometrically in solution. The organic-soluble TPAP' ((n-Pr[sub 4]N)[RuO[sub 4]]) with N-methylmorpholine N-oxide is an efficient selective catalyst for converting primary alcohols to aldehydes and secondary alcohols to ketones. The [RuO[sub 4]][sup [minus]] ion can be generated in aqueous base at pH 11 from aquated ruthenium trichloride with excess bromate, and this reagent will catalytically oxidize primary alcohols, activated alkyl halides, aldehydes, 1,2-diols, and nitroalkanes to carboxylic acids, while secondary alcohols and secondary halides are oxidized to ketones, bromate being the cooxidant. These oxidations are compared with those effected catalytically by trans-[Ru(OH)[sub 2]O[sub 3]][sup 2[minus]] in aqueous base at pH 14 with persulfate as cooxidant. A new preparation for organic-soluble salts of [RuO[sub 4]][sup [minus]] avoiding the use of RuO[sub 4] is described. 29 refs., 1 tab.

ヘテロポリ酸触媒を用いる過酸化水素酸化

Hydrogen peroxide oxidation of various organic substrates can be achieved by the use of heteropoly acids (HPA) combined with cetypyridinium chloride (CPC) as catalyst. Tris (cetylpyridinum) 12-tungstophosphate (CWP), [π-C5H5N+ (CH2) 15CH3] 3 (PW12O40) 3-, prepared from 12-tungstophosphate (WPA) and 3 equivalents of CPC, catalyzed the epoxidation of olefins and allylic alcohols in chloroform, and α, β-unsaturated carboxylic acids in water. sec-Alcohols and diols containing sec-hydroxy groups were oxidatively dehydrogenated by CWP-H2O2 system in t-butyl alcohol to give the corresponding ketones. Under the same conditions, α, ω-diols were converted to lactones in fair yields. This catalyst-oxidant system was also efficient for the oxidative cleavage of carbon-carbon bonds of vic-diols and olefins. Peroxo-heteropoly acids, derived from HPA, CPC and H2O2, oxidized stoichiometrically or catalytically a wide varaiety of substrates in a similar manner as above.

Oxidation of Various Organic Substrates by Three Xanthomonas spp.

Oxidation of Various Organic Substrates by Three Xanthomonas spp.