Oxidation Of Aromatic Amines Research Articles

Highly ordered TiO2 nanotube arrays and photoelectrocatalytic oxidation of aromatic amine

Self-organized Ti/TiO2 nanotubular array electrodes may be achieved by simple electrochemical anodization of Ti foil in NH4F/glycerol water solution. The photocurrent on nanotubular layers is remarkably improved in relation to that obtained on comparable nanoporous TiO2 films created by a sol gel process. The anatase form is priori in the highly ordered TiO2 annealed at 450°C which improves its photoactivity. Both electrodes promote complete degradation of the investigated aromatic amine ODAN (4,4′-oxydianiline) after 120min of photoeletrocatalytic oxidation with potential of 1.5V and UV irradiation. But, the ODAN mineralization is about 50% more efficient on nanotubular electrodes. The best experimental conditions were found to be pH 2.0 and 0.1molL−1 Na2SO4 when the photoelectrode was biased at +1.5V (vs. SCE). Complete mineralization of the aromatic amine content (100% TOC reduction) was achieved after 2h. Effects of other electrolytes, pH, amine concentration and applied potentials also have been investigated and are discussed.

A Novel Synthesis and Characterization of Titanium Superoxide and its Application in Organic Oxidative Processes

A novel, exceptionally stable titanium superoxide radical ion was prepared and its structure determined by FTIR, ESR, Raman spectroscopy, X-ray diffraction, thermogravimetric/differential thermal analysis and elemental analysis. This heterogeneous catalyst has been found to be effective for the selective oxidation of aromatic amines and phenols to the corresponding nitro aromatics and p-quinones, respectively. In addition, this non-toxic, inexpensive and reusable catalyst has also been used in aminobromination of olefins, which proceed to give the 1, 2-bromoaminated anti-Markovnikov product. A brief account of these results is summarized in this review.

Experimental design for the study and optimization of the effect of different surfactants on the spectrophotometric determination of sulfide based on phenothiazine dye production

In the present work the effect of three different surfactants Triton X-100, cetyltrimethylammonium bromide (CTAB) and sodium dodecylesulfate (SDS) on the spectrophotometric determination of sulfide based on phenothiazine dye production from phenyl-p-diamine (PPD) is studied. The main step for phenothiazine dye production is the oxidation of aromatic p-substituted amine to yield iminoquinone free-radical intermediary. Fe3+ in acidic media is used for oxidation purposes. Electron donor groups in the p-position of aromatic ring of amines are decisive for free-radical stabilization, leading to an increased dye production rate and the analytical sensitivity. Preliminary studies showed that, the analytical signal was increased in the presence of SDS, CTAB and Triton X-100; but among the surfactants studied, SDS and Triton X-100 had a significant effect on the spectrophotometric determination of sulfide based on phenothiazine dye production. The effects of various experimental parameters in this reaction was investigated using central composite design. The experimental design was done at five levels of operating parameters. As a model surfactant, the concentration of SDS, amine, Fe3+ and H2SO4 were optimized simultaneously. The effects of Triton X-100 and CTAB as non-ionic and cationic surfactant, respectively, were investigated using a one variable at a time optimization method. The linear range for the determination of sulfide in the presence of SDS and Triton X-100 was 0.1–2 μg ml−1 and that in presence of CTAB was 0.2–2.0 μg ml−1. The proposed method was applied successfully for the determination of sulfide in different spiked real samples.

Redox-mediated oxidation and removal of aromatic amines from polluted water by partially purified bitter gourd ( Momordica charantia) peroxidase

Here, the role of bitter gourd peroxidase has been investigated for the treatment of water contaminated with aromatic amines. Most of the aromatic amines were recalcitrant to the action of bitter gourd peroxidase. However, these aromatic amines were oxidized by bitter gourd peroxidase in the presence of a redox mediator, o-dianisidine HCl. The maximum oxidation of aniline was found to be in the buffer of pH 5.0 at 40 °C in the presence of 0.5 mM H 2O 2 and 0.15 mM o-dianisidine HCl. Aromatic amines oxidized and removed from wastewater were 65% aniline, 50% m-toluidine, 86% m-chloroaniline, 54% p-aminobenzoic acid, 61% diphenylamine and 95% N,N-dimethylaniline. Benzidine and p-nitroaniline were recalcitrant to the action of this enzyme even in the presence of o-dianisidine HCl. Complex mixtures of aromatic amines were treated by bitter gourd peroxidase. These mixtures were removed to varying extent, mixtures A, B and C were oxidized to 59%, 56% and 62%, respectively. Mixtures D, E and F were marginally oxidized to 30%, 14% and 16%, respectively.

Electroorganic synthesis : A novel route of green synthesis

Electroorganic synthesis of alkanes, alkenes and esters by anodic decarboxylation of potassium salt of palmitic acid, stearic acid, lauric acid and myristic acid, amines by reduction of aromatic nitro compounds, pinacols by reduction of carbonyl compounds, aromatic dimmers by oxidation of aromatic amines, 1,3,4-oxadiazole derivatives by electrocyclization of semicarbazone and acylthiosemicarbazone, aldol condensation of aldehydes, and acetamidation of aromatic compounds were carried out at platinum plate in undivided electrochemical cell at desired potential using simple solvent and supporting electrolyte. All the reactions were carried out at room temperature by using small amount of electricity without involvement of toxic chemicals.

Selective Oxidation of Aromatic Amines to Nitro Derivatives using Potassium Iodide‐tert‐Butyl Hydroperoxide Catalytic System

AbstractThe direct oxidation of aromatic primary amines to the corresponding nitro compounds selectively in 47–98% yields has been achieved by using potassium iodide as catalyst and tert‐butyl hydroperoxide as the external oxidant. The present catalytic system works well for both electron‐rich and electron‐poor substrates.

Isoquinolinium bromochromate; new, efficient and stable reagent for oxidation of aromatic amines and phenols

The new chromium(VI) oxidizing reagent isoquinolinium bromochromate (IQBC) was prepared and characterized. This new compound has been found to be an efficient reagent for oxidation of primary amines and phenols. The oxidation of primary amines and phenols with isoquinolinium bromochromate proceeded smoothly to afford corresponding azobenzenes and quinones in good to excellent yield. The synthesized isoquinolinium bromochromate is more ideal reagent, with number of specifications including higher yield, mild conditions and easy preparation. The results obtained with isoquinolinium bromochromate are satisfactory and suggest that this new reagent is valuable addition to the existing chromium(VI) reagents.

B···π-aromatic and C–H···B interactions in co-crystals of aromatic amine N-oxides with p-phenylenediboronic acid

Co-crystals of p-phenylenediboronic acid with four aromatic N-oxides namely pyridine N-oxide, quinoline N, N′-dioxide, isoquinoline N, N′-dioxide and 4,4′-dipyridine N, N′-dioxide are prepared and are structurally characterized. The stacking pattern in each case is found to be different. An interesting stacking effect that, sandwiches the boronic acid groups by pyridine N-oxide rings and associated through η 2 and η 3 type B–π interactions is presented. In the structures of co-crystals of aromatic amine N-oxides with p-phenylenediboronic acid B···π aromatic and C–H···B interactions are observed.

ChemInform Abstract: Oxidation of Primary Aromatic Amines under Irradiation with Ultrasound and/or Microwaves.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Oxidative ortho-C-N Fusion of Aniline by OsO4. Isolation, Characterization of Oxo-Amido Osmium(VI) Complexes, and their Catalytic Activities for Oxidative C−C Bond Cleavage of Unsaturated Hydrocarbons

In an unusual reaction of osmium(VIII) oxide with p-substituted aromatic amines (X-C(6)H(4)-NH(2), where X = Me, H, Cl) in heptane afforded the brown osmium(VI)-oxo complexes [OsO(L)(2)] (1a-c, L = N-aryl-1,2-arylenediamide) in moderate yields. The ligand L is formed in situ via oxidative ortho-C-N fusion of arylamines. The reaction occurs in an inert atmosphere, and a part of Os(VIII) is used up for the oxidation of aromatic amine. Single crystal X-ray structure of a representative complex 1a is solved. The structural analysis has authenticated the ortho-C-N fusion of ArNH(2) resulting in formation of the diamide ligand, L. The complex as a whole is penta-coordinated, and the coordination sphere has a distorted square pyramidal geometry (tau = 0.26). A similar reaction of osmium(VIII) oxide with the preformed N-phenyl-1,2-phenelene diamine produced the complex 1a in nearly quantitative yield. The substituted phenazine, 5-phenyl-3-phenylimino-3,5-dihydro-phenazine-2-ylamine, is obtained as a byproduct of the latter reaction. The complexes, 1a-c, can be reduced in a reversible one-electron step, as probed by cyclic voltammetry. The one electron reduced paramagnetic Os(V) intermediate is, however, Electron Paramagnetic Resonance (EPR) silent. Solution spectra of the osmium complexes show several multiple transitions in the UV-vis region. Density functional theory calculations were employed to confirm the structural features and to support the spectroscopic assignments. The complex 1a catalyzes oxidation of a wide variety of unsaturated hydrocarbons like alkenes, alkynes, and aldehydes to the corresponding carboxylic acids in the presence of tert-butylhydroperoxide (TBHP) efficiently at room temperature.

Oxidation of Primary Aromatic Amines under Irradiation with Ultrasound and/or Microwaves

The oxidation of primary aromatic amines, p-methylaniline, p-ethylaniline and p-chloroaniline to the corresponding azo- and azoxy-compounds has been observed in ultrasound and/or microwaves systems. The individual irradiation of microwaves and its simultaneous irradiation with ultrasound obviously elevate the conversion of amines, as compared with the individual irradiation of ultrasound and the heating in a plain water bath. However, the formation of formamidine resulted in poor selectivity toward azo and azoxy products in the presence of dimethylformamide (DMF).

The catalytic performance of Mn-tetraarylporphyrins in the highly selective oxidation of primary aromatic amines to azo compounds by Bu 4NHSO 5

The catalytic activity of Mn(TPP)OAc/imidazole system in the oxidation of aromatic amines using Bu 4NHSO 5 in CH 3CN, provides a rapid and highly selective method for the preparation of symmetrical azoarenes, in high/excellent yield (78–96%) and short time (<5 min). The selectivity of the reaction depends remarkably on both the axial ligand and the nature of the solvent. Electron-deficient anilines are oxidized slowly and yield azoxy arenes as the main product. The presence of an electron-donating group on the phenyl ring of both the aromatic amine and the porphyrin ligand of the catalyst enhances the oxidative reactivity of the amine as well as the catalytic activity of the Mn-catalyst. The high turn over rates obtained for Mn-porphyrin reflect the efficiency as well as the relative stability of this biomimetic catalyst towards oxidative degradation. Some evidences for the participation of an Mn-oxo species as active oxidant in this catalytic process have been obtained.

CuCl-catalyzed aerobic oxidative reaction of primary aromatic amines

The oxidations of primary aromatic amines were investigated. Cuprous chloride-air system can catalyze the oxidation of primary aromatic amines to azo derivatives, anils, and/or quinone anils. The experimental procedure is simple and the products could be easily isolated in high yields.

Selective N-oxidation of aromatic amines to nitroso derivatives using a molybdenum acetylide oxo-peroxo complex as catalyst

The molybdenum acetylide oxo-peroxo complex obtained in situ by the treatment of the corresponding molybdenum acetylide carbonyl complex, CpMo(CO) 3(C CPh); Cp = η 5-C 5H 5 with H 2O 2, has been used as an efficient catalyst for selective N-oxidation of primary amines to nitroso derivatives. Excellent amine conversion (up to 100%) and very high selectivity for nitroso compounds (99%) have been obtained using 30% hydrogen peroxide as an oxidant. The oxo peroxo Mo(VI) complex has also been found to be very active for the oxidation of various substituted primary aromatic amines with electron donating as well as electron withdrawing substituents on the aromatic ring.

Oxidations ofN-(3-Indoleethyl) Cyclic Aliphatic Amines by Horseradish Peroxidase: The Indole Ring Binds to the Enzyme and Mediates Electron-Transfer Amine Oxidation

Although oxidations of aromatic amines by horseradish peroxidase (HRP) are well-known, typical aliphatic amines are not substrates of HRP. In this study, the reactions of N-benzyl and N-methyl cyclic amines with HRP were found to be slow, but reactions of N-(3-indoleethyl) cyclic amines were 2-3 orders of magnitude faster. Analyses of pH-rate profiles revealed a dominant contribution to reaction by the amine-free base forms, the only species found to bind to the enzyme. A metabolic study on a family of congeneric N-(3-indoleethyl) cyclic amines indicated competition between amine and indole oxidation pathways. Amine oxidation dominated for the seven- and eight-membered azacycles, where ring size supports the change in hybridization from sp3 to sp2 that occurs upon one-electron amine nitrogen oxidation, whereas only indole oxidation was observed for the six-membered ring congener. Optical difference spectroscopic binding data and computational docking simulations suggest that all the arylalkylamine substrates bind to the enzyme through their aromatic termini with similar binding modes and binding affinities. Kinetic saturation was observed for a particularly soluble substrate, consistent with an obligatory role of an enzyme-substrate complexation preceding electron transfer. The significant rate enhancements seen for the indoleethylamine substrates suggest the ability of the bound indole ring to mediate what amounts to medium long-range electron-transfer oxidation of the tertiary amine center by the HRP oxidants. This is the first systematic investigation to document aliphatic amine oxidation by HRP at rates consistent with normal metabolic turnover, and the demonstration that this is facilitated by an auxiliary electron-rich aromatic ring.

ChemInform Abstract: In situ Generation of Nitroso Compounds from Catalytic Hydrogen Peroxide Oxidation of Primary Aromatic Amines and Their One‐Pot Use in Hetero‐Diels—Alder Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tungsten‐ and Molybdenum‐Based Coordination Polymer‐Catalyzed N‐Oxidation of Primary Aromatic Amines with Aqueous Hydrogen Peroxide

AbstractRecyclable tungsten‐ and molybdenum‐based coordination polymers efficiently catalyzed the oxidation of primary aromatic amines to the corresponding nitroso derivatives with 30 % aqueous hydrogen peroxide in high yields at room temperature.

Initiation and inhibition of free-radical processes in biochemical peroxide systems: A review

The role of complexes containing oxygen or peroxide in monooxygenase systems and models thereof, as well as in peroxidase- and quasi-peroxidase-catalyzed processes, has been reviewed. Pathways of conversion of these intermediate complexes involving single-electron (radical) and two-electron (heterolytic) mechanisms are dealt with. Coupled peroxidase-catalyzed oxidation of aromatic amines and phenols is analyzed; inhibition and activation of peroxidase-catalyzed reactions are characterized quantitatively. Oxidation of chromogenic substrates (ABTS, OPD, and TMB) in the presence of phenolic inhibitors or polydisulfides of substituted phenols is characterized by inhibition constants (Ki, micromol). Activation of peroxidase-catalyzed oxidation of the same substrates is characterized by the degree (coefficient) of activation (alpha, M(-1)), which was determined for 2-aminothiazole, melamine, tetrazole, and its 5-substituted derivatives. Examples of applied use of peroxidase-catalyzed enzyme and model systems are given (oxidation of organic compounds, chemical analysis, enzyme immunoassay, tests for antioxidant activity of biological fluids).

In Situ Generation of Nitroso Compounds from Catalytic Hydrogen Peroxide Oxidation of Primary Aromatic Amines and Their One‐Pot Use in Hetero‐Diels–Alder Reactions

AbstractA method for in situ generation of nitroso compounds from organoselenium‐catalyzed oxidation of anilines by hydrogen peroxide was developed. The generated nitroso compounds were subsequently used in hetero‐Diels–Alder reactions. A variety of oxazines were synthesized in reasonable to good yields by this one‐pot procedure using primary aromatic amines with different substituents and various conjugated dienes. This strategy might facilitate the current methodologies for nitroso chemistry since no isolation or purification of the nitroso compounds is required. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

Water as an Efficient Solvent for Oxygenation Transformations with 34% Hydrogen Peroxide Catalyzed by some Heteropolyoxometalates

A highly efficient, selective, fast, and cheap protocol is developed for oxidation of aromatic amines and alcohols utilizing 34% hydrogen peroxide in water catalyzed by some W- and Mo-based heteropolyoxometalates. Findings showed that dodecatungstophosphoric acid, H3PW12O40, was the most efficient catalyst in the examined oxidation reactions. This methodology may prove to be a valuable alternative for eco-friendly green oxidation. Inherent simplicity, easy work up, and using regenerable catalysts were other key aspects of this oxidation protocol.