Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic Compounds by Potassium Permanganate

Summary. The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions that is, in theory, infinitely sustainable.     

Solid Phase Derivatizations in HPLC: Polymeric Permanganate Oxidations of Alcohols and Aldehydes in HPLC-SPR

Abstract

On-line or off-line oxidations of various alcohols, aldehydes, and ketones can now be performed in conjunction with high performance liquid chromatography (HPLC), utilizing a newly developed polymeric permanganate solid phase reactor (SPR). These derivatization reactions are compatible with most reversed phase and normal phase solvents for HPLC separations, and many of these oxidations can be accomplished in real-time, on-line, at or above room temperature. Such HPLC-SPR approaches for chemical modifications and derivatizations of various oxidizable analytes provide a useful and quite practical newer approach for the HPLC-ultraviolet (UV) detection of appropriate analyte species. Difference chromatography, often with improved UV detection, can be used to confirm the suspected presence of a particular oxidizable analyte in a complex sample matrix. All of these solid phase derivatizations utilize conventional, commercially available HPLC instruments and accessories. These HPLC-SPR oxidation methods for chemical derivatization have also been applied to certain real world samples, in order to demonstrate the overall value and applicability of such analytical approaches.     

Kinetics and Mechanism of the Autocatalyzed Oxidation of Theophylline by Permanganate in Aqueous Perchloric Acid Medium

The reaction kinetics for the oxidation of theophylline by permanganate ions have been investigated in perchloric acid medium using spectrophotometric techniques at 25?^°C, and at constant ionic strength 1.60 mol?dm^?3, under pseudo first order conditions. An autocatalyzed reaction is observed due to one of the products formed is Mn(II). The orders with respect to theophylline and Mn(VII) were both found to be unity, whereas fractional order is observed with respect to the autocatalyst, Mn(II). The rate of the reaction increases as the concentration of acid increases, but the order with respect to acid concentration is less than unity. The influence of temperature on the rate of reaction was studied. Based on the experimental results a suitable mechanism is proposed. The activation and thermodynamic parameters were determined with respect to slow reaction step.     

Formal Bleaching Kinetics of Acid Blue 80 in Weakly Acidic,Neutral, and Basic Aqueous Media

General kinetic relations were established for the first step of oxidation of Acid Blue 80 in weakly acidic, neutral and basic media in the following systems: Fe²⁺-H₂O₂, Mn²⁺-HCO₃ ^--H₂O₂, and Cu²⁺-phenanthroline-H₂O₂. The rate constant for the reaction of hydroxyl radical with the dye and the dependence of the degree of bleaching upon oxidant and catalyst concentrations were determined.     

Kinetics and Mechanism of Oxidation of Captopril by Hexacyanoferrate(III) in Aqueous Acidic Medium

Captopril (Capt, 1-[2(s)-3-mercapto-2-methyl-1-oxopropyl]-l-proline) was oxidized by hexacyanoferrate(III) (HCF). The kinetics of the oxidation was studied spectrophotometrically at 420 nm. The reaction was found to be first order in [HCF] and [Capt] and to have a negative fractional order in [H⁺]. Oxidation was followed by generation of a free radical from captopril, and the oxidative product of catpotpril was identified as captopril disulfide. It was characterized by IR, GCMS and ESI–MS spectra. Initially added product, hexacyanoferrate(II), retarded the rate of reaction with an order of ?0.5. The retarding effect of added [H⁺] indicated that unprotonated hexacyanoferrate(III) is the active species. A suitable free radical mechanism was proposed. The rate law was derived and verified.     

Rearrangements of Neoclovene Epoxides in Acidic Media

Rearrangements of neoclovene epoxides in the presence of a solid superacid ZrO₂/SO₄ ^{2 -} and in formic acid were investigated. In the latter case a ketone was obtained with a previously unknown carbon skeleton. The most probable pathway of its formation was derived from calculations by molecular mechanics and quantum-chemical methods.     

Kinetics and Mechanism of Oxidation of Adipic Acid by Ce(IV) Ion in Acidic Medium

Kinetic study of oxidation of adipic acid by Ce(IV) ion in aqueous solution of sulphuric acid shows that the reaction follows first order kinetics in both Ce(IV) and adipic acid and the over all reaction order ascertained is two. The specific rate constant increases with an increase in the concentration of adipic acid. Effects of hydrogen ion concentration, bisulphate ion and temperature have been studied in detail. Various kinetic parameters have been computed. The experimental findings are consistent with the mechanism involving rapid resersible formation of an activated complex between Ce(IV) and adipic acid followed by a rate determining step involving C-C bond fission.     

Kinetics and Mechanism of Oxidation of Dimethyl Sulfoxide with Benzoyl Peroxide in Superbasic Media

Oxidation of dimethyl sulfoxide with benzoyl peroxide in some dipolar aprotic solvents and superbasic media was studied. The kinetic parameters were correlated with the main physicochemical characteristics of solvents. The oxidation rate grows with increasing donor number and polarizability of the solvent. A two-step scheme of dimethyl sulfoxide oxidation with benzoyl peroxide in superbasic media was suggested, involving preliminary cleavage of the peroxide to perbenzoate with the base. In the reaction, sodium tert-butylate is preferable over sodium hydroxide.     

Synthesis of Pd-Cu Bimetallic Electrocatalyst for Ethylene Glycol and Glycerol Oxidations in Alkaline Media

PdCu/C (XC-72) electrocatalyst was synthesized by a chemical reduction method using ethylene glycol as reaction media, polyvinylpyrrolidone as surfactant and sodium borohydride as reducing agent. Vulcan carbon XC-72 was employed as support and added through the PdCu synthesis procedure; further, Pd commercial (Pd/C, 20% ETEK) was used for comparison purposes. Physicochemical characterization consisted in XRD, XRF, EDS and TEM analyses. TEM micrographs showed the presence of semi-spherical nanoparticles with a particle distribution around 6 nm. X-ray diffraction patterns showed the typical face-centered cubic structure of Pd materials for commercial Pd and revealed a low crystallinity for PdCu/C. The XRF analysis showed a mass metal composition of 81% Pd and 19% Cu. EDS analysis was made to single particles exhibiting an average elemental composition of 92% Pd and 8% Cu. The electrocatalytic activity of PdCu/C and Pd/C was evaluated by cyclic voltammetry experiments toward ethylene glycol and glycerol oxidations using three concentrations (0.1, 1 and 3 M) and 0.3 M KOH as electrolyte. These experiments exhibited the superior performance of PdCu compared with commercial Pd by means of current densities associated to the electro-oxidation reactions where values at least 3-fold higher than Pd/C were found.     

Synthesis and Crystal Structures of Copper(I) Complexes with N-Allylhexamethylenetetraminium Chloride Obtained in Different Acidic Media

The crystals of [(CH₂)₆N₄(C₃H₅)]Cu₂Cl₃ (I), [(CH₂)₆N₄(C₃H₅)]Cu₂Cl₃ (II), and [(CH₂)₆N₄(C₃H₅)]CuCl₂ (III) complexes were electrochemically synthesized (ac) from CuCl₂ · 2H₂O and N-allylhexamethylenetetraminium chloride in ethanol solutions at pH 6, 4.5, and 3. Their structures were determined using X-ray diffraction analysis (DARCh diffractometer, MoK radiation, /2 scan mode). Complex Icrystallizes in the monoclinic system: space group A2/a, a = 24.812(6) Å, b = 8.855(3) Å, c = 12.080(2) Å, = 89.21(3)°, and Z = 8. Complex II crystallizes in the triclinic system: space group P , a = 7.618(2) Å, b = 7.048(2) Å, c = 13.150(3) Å, = 97.50(2)°, = 92.70(2)°, = 100.74(2)°, and Z = 2. The crystals of complex III are orthorhombic: space group Pmn2₁, a = 7.478(2) Å, b = 8.827(2) Å, c = 9.662(3) Å, Z = 2. The organic cation in complex I acts as a tridentate ,,-ligand; that in complex II, as a bidentate ,-ligand. In complex III, the organic cation is involved in coordination with the copper(I) atom only through one nitrogen atom.     

Characteristics of Template Formation in Silica in Acidic Media

Characteristics of template formation in silica at pH < 0.1 in the presence of a surface active substance (cetyltrimethylammonium bromide or chloride) have been investigated. Depending on the acidity of the reaction medium and some other factors, the synthesis of spontaneously growing particles of templated silica at interfacial surfaces led to the formation of fibers, spirals, spheres, and other forms, most of which appeared as hexagonally ordered bodies of revolution. It is possible to detemplate these forms of silica and to transform them to mesoporous molecular sieves without destroying their structures.     

Kinetics and Mechanism of the Liquid-Phase Oxidation of 10-Dihydro-9-ketoanthracene in Basic Aprotic Media

The kinetics of the liquid-phase oxidation 10-dihydro-9-ketoanthracene (anthrone) by molecular oxygen was studied in dimethylsulfoxide. Anthrone was found to undergo facile oxidation to give anthraquinone in virtually quantitative yield in this highly basic, polar solvent, while the oxidation rates are much lower in acetonitrile and dimethylformamide, which are less polar solvents. A kinetic scheme for this reaction was proposed.     

偶氮染料在酸性介质中的电还原性质

研究了4个偶氮染料在酸性介质中的电还原性质。偶氮基在酸性介质中的还原均为不可逆四电子一步全还原。邻、对位上有吸电子基(如—CO_2Bu-n)的偶氮基较间位有吸电子基时更易被还原。分子中同时含有偶氮基和硝基时,偶氮基先被还原。     

Kinetics of the Oxidative Degradation of rac-Serine by Aqueous Alkaline Permanganate

Summary.  The kinetics of the oxidation of rac-serine by permanganate in aqueous alkaline medium was studied spectrophotometrically. The reaction showed first order kinetics in permanganate ion concentration and an order less than unity in rac-serine and alkali concentration. Increasing ionic strength and decreasing dielectric constant of the medium increase the rate. The oxidation reaction proceeds via an alkali-permanganate species which forms a complex with rac-serine. The latter decomposes slowly, followed by a fast reaction between a free radical of rac-serine and another molecule of permanganate to give the products. There is a good agreement between the observed and the calculated rate constants under different experimental conditions. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism. Received October 15, 1999. Accepted (revised) December 15, 1999     

Rearrangements of Epoxides of Some Acyclic Terpenoids in Acidic Media

2,3-Epoxygeraniol undergoes dissimilar rearrangements in contact with liquid superacids at low temperature or on solid superacids at room temperature due to different location of the arising cationic center depending on the superacid character. 2,3-Epoxynerol, 6,7-epoxycitronellol, and 6,7-geranyl acetate on ZrO₂SO₄^2- afford the corresponding ketones via epoxy ring opening followed by 1,2-hydride shift. With 6,7-geranyl acetate 7-oxanobornane formed as a minor product. The mode of generation of the cationic center (either the olefin protonation or the epoxy ring opening) affects the rearrangement direction at similar conditions.     

高锰酸钠去除水中苯胺的不可逆过程热力学研究

苯胺在城市污水中大量存在,常采用氧化剂去除水中的苯胺.本文利用不可逆过程热力学理论,对高锰酸钠去除水中苯胺的动力学进行了研究,得到了与实验数据拟合较好的三次关系式.结果表明,在PH值及温度恒定的条件下,高锰酸钠及苯胺的初始浓度对苯胺的去除效果有影响.     

Hydrolysis of Chloro(silyl)olefins in Neutral and Acidic Media

Action of water on chloro[chloro(alkoxy)silyl]olefins with various number of chlorines in the unsaturated moiety was studied in acidic and neutral media. Linear and cyclic oligosiloxanes with unsaturated chlorine-containing groups were obtained. Correlation between the hydrolytic stability of the Si-Csp ² bond and the structure of the starting chlorosilylolefin was explored.     

Kinetics of the Oxidation of Monosaccharides with Acidic Bromate and N-Bromosuccinimide

Abstract

In earlier studies on the oxidation of monosaccharides, we measured the rates of the oxidation of three aldohexoses, two ketohexoses and three aldopentoses with V(V),¹ Ce(IV)²Cr(VI)³ and MII(VII).⁴We now report on the corresponding oxidations with bromate ion and N-bromosuccinimide (NBS) as oxidants. To our knowledge, only kinetic studies of oxidations of ribose with BrO₃-in aqueous H₂O₄ ⁵ and aldoses with NBS in 10% AcOH - H₂SO₄ ⁶ have been reported. Because oxidation of carbohydrates is subject to HSO₄- ion catalysis, HClO₄ was used, as in our earlier studies, in the present investigation to minimize the number of different catalyzing species.     

Transformations of 6,7-Epoxy Derivatives of Citral and Citronellal in Various Acidic Media

The transformations of 6,7-epoxy derivatives of widely spread in the nature unsaturated aldehydes, citral and citronellal, in various acidic media both under conditions of homogeneous and heterogeneous catalysis were investigated. A number of previously unknown products belonging to different classes of organic compounds was obtained. Probable mechanisms of the products formation are discussed.