Oxidation Of Aromatic Amines Research Articles

ChemInform Abstract: Oxidation of Aromatic Amines with Chromyl Chloride. Part 1. Oxidation of Aromatic Primary Amines.

AbstractThe oxidation of aromatic amines, e.g. (Ia)‐(Io), with chromyl Chloride yields solid intermediates (studied in detail in the following paper), affording mixtures of the azobenzenes (II) and the quinone derivatives (III)‐(VI) on hydrolysis.

ChemInform Abstract: Oxidation of Aromatic Amines with Chromyl Chloride. Part 2. Studies on the Intermediate Solid Adducts.

AbstractElemental analysis, IR and magnetic measurements are employed to characterise the intermediates of the title reaction (its application is described in the preceding paper).

ChemInform Abstract: Oxidation of Aromatic Amines by N‐Chloroanilides. Direction of Polarity of the Nitrogen ‐ Chlorine Bond

ChemInform Abstract: Oxidation of Aromatic Amines by N‐Chloroanilides. Direction of Polarity of the Nitrogen ‐ Chlorine Bond

Two-electron oxidation of N, N, N′, N′-tetramethyl naphthidine in acetonitrile The reactivity of its dication to aromatic nucleophilic substitution by pyridine

The electrochemical oxidation of N, N, N′, N′-tetramethyl-1,1′-naphthidine (TMN), has been studied at the platinum electrode in acetonitrile. Cyclic voltammetry and coulometric studies show that, in neutral acetonitrile, TMN oxidizes to a stable dication (TMN 2+), in a reversible two-electron transfer. The factors that could contribute to this unusual behaviour I the anodic oxidation of aromatic amines are discussed. Electrochemical studies in acetonitrile, but with the addition of acid (anhydrous trifluoroacetic acid) and of bases (pyridine and 2,6-lutidine) were also performed. In acid medium, the anodic oxidation of TMN shows behaviour similar to the one observed for homologous compounds such as benzidines. However, in basic medium and when the base, such as pyridine, can act as a nucleophile, a reaction is observed with TMN 2+. The product is a pyridinium salt, resulting from an aromatic nucleophilic substitution on the naphthalene moiety. The kinetics of this reaction were studied by electrochemical and spectroscopic methods.

Infrared and thermal studies of 5,6-benzoquinoline N-oxide complexes of oxozirconium(IV)

We have recently reported the infrared and thermal properties of 5,6-benzoquinoline complexes of higher valent metal ions including oxozirconium(IV) [l]. Aromatic amine N-oxides are potential coordinating agents [2-51. Thus, it is worthwhile to study the coordinating ability of 5,6-benzoquinoline N-oxide. In the present communication, we describe the synthesis, infrared and thermal behaviour of oxozirconium(IV) complexes of 5,6-benzoquinoline N-oxide (Benzquo).

Oxidation of aromatic amines with chromyl chloride-I : Oxidation of aromatic primary amines

The oxidation of aromatic primary amines with chromyl chloride in carbon tetrachloride or chloroform, results in the formation of intermediate solid adducts (Etard adducts) which, on hydrolysis, give azobenzenes( 1), 1,4-benzoquinones( 2),anilino-1,4-benzoquinones( 3), 1,4-benzoquinone anils( 4)and anilino-1,4-benzoquinone anils ( 5) in yields which depend on the position, nature and degree of substitution of the ring.

Oxidation of aromatic amines with chromyl chloride-II : Studies on the intermediate solid adducts

Oxidation of aromatic primary amines with chromyl chloride results in the formation of intermediate solid Etard adducts (C. Nallaiah and J.A. Strickson, Tetrahedron 42,4083 ( 1986)). Elemental analysis of the adducts indicates that the anilines, which give 1,4-benzoquinone anils in good yields, form adducts close to a 1:1 stoichiometry with the oxidant while those forming 1,4-benzoquinones in substantial yields form 1:2 adducts. Magnetic measurements on the adducts reveal that chromium atoms are mainly present m the oxidation state chromium(IV). IR studies indicate that the adducts comprise of 1,4-benzoquinone imines and di-imines as ligands and that giant molecules are formed by chloro and hydroxy bridges.

2-Nitrofluoren-9-one: a unique mutagen formed in the photo-oxidation of 2-aminofluorene.

Exposure of solutions of 2-aminofluorene (2-AF, dissolved in dimethylsulfoxide) to near ultraviolet light (u.v.a. wavelengths of 320-400 nm) results in the formation of a variety of photo-products, several of which are direct-acting mutagens in the Ames/Salmonella standard-plate assay. Previously published results from our laboratory have described the chemical identification and kinetics of formation of two of these photo-induced mutagens, 2-nitrosofluorene and 2-nitrofluorene. In this report we present recent data concerning the isolation and chemical identification of another mutagenic photoproduct of u.v.a.-irradiated 2-AF, 2-nitrofluoren-9-one (2-NO2F-9-one). Data are also presented concerning the kinetics of phototransformation of 2-aminofluoren-9-one, an early-appearing and predominant photoproduct in u.v.a.-irradiated solutions of 2-AF, into 2-NO2F-9-one. It is well established that N-oxidation is a critical step in the biotransformations (i.e. enzymatic metabolism) of primary aromatic amines into proximate mutagens/carcinogens. In addition to u.v.a.-mediated N-oxidation of aromatic amines, selective ring photo-oxidation can also occur, resulting in, for example, the production of a carbonyl group at the 9-position of the fluorene molecule. The formation of mutagenic 2-NO2F-9-one in the photochemical oxidation of 2-AF appears to be unique to this process.

Oxidation of aromatic amines by N-chloroanilides. Direction of polarity of the nitrogen–chlorine bond

The effect of substituents in the aromatic ring as well as in the acyl moiety of some N-chloroanilides [XC6H4N(Cl)COR; X =m-Cl, p-Br, H, m-Me, p-Me; R = Me, Pri, Et, PhCH2, Ph] on the kinetics of oxidation of aniline and p-toluidine has been studied in 1 : 1 ethanol–water (v/v) at various temperatures. The reactivity decreases in the following order: m-Cl > p-Br > H > m-Me > p-Me; Ph > PhCH2 > Me > Et > Pri. For p- and m-substituted N-chloroacetanilides, a correlation with the Hammett σ parameter exists. On the other hand, the Taft equation gives an excellent fit with the rate data for five N-chloroacylanilides. The results are interpreted in terms of bimolecular interaction of the positive chlorine of the N–Cl bond and the amino nitrogen.

Complexes of TlClI2with Aromatic Amine Oxides

Abstract The following compounds: TlClI2 (PyO)2; TlClI2(2-PicO)2; TlClI2(3-PicO)2; TlClI2(4-PicO)2; TlClI2(4-Cl-PyO)2; TlClI2 (4-CN-PyO)2; TlClI2(4-NO2-PyO)2 and TlClI2 (4-CH3O-PyO)2 have been prepared and characterized by elemental analysis. The solids behave as monomers and non-electrolytes in solution. Possible molecular structures are given on the basis of 1H NMR and lR spectra, with particular attention on the νTl-X and νTl-O strectching modes.

Infrared and thermal studies of oxozirconium(IV) complexes of 2-acetyl pyridine N-oxide

The metal ion complexes of pyridine N-oxides have been the subject of four recent reviews [1–4]. Comparatively little is known about the compounds of oxozirconium(IV) with aromatic amine N-oxides [5]. Kidani et al. [6] reported that 2-acetyl pyridine coordinates in a bidentate manner. A related ligand, 2-acetyl pyridine N-oxide, can also coordinate either in a monodentate or bidentate form. The ligational behaviour of 2-acetyl pyridine N-oxide towards some metal ions has already been reported by West and co-workers [7,8]. In the present communication, the metal complexes formed by 2-acetyl pyridine N-oxide (APO) with oxozirconium(IV) salts are reported.

Photochemical oxidation of 2-aminofluorene: Correlation between the induction of direct-acting mutagenicity and the formation of nitro and nitroso aromatics

The kinetics of near ultraviolet light-mediated phototransformation of 2-aminofluorene (2-AF) was studied using high performance liquid chromatography (HPLC) and the Ames/Salmonella mutagenicity bioassay. Employing tester strains TA98, TA1538, and the nitroreductase-deficient TA98NR without the addition of exogenous metabolic enzymes, we were able to detect and discriminate between the UVA exposure-dependent formation of two stable photoproducts, 2-nitrosofluorene (2-NOF) and 2-nitrofluorene (2-NO 2F). Mutagenicity of irradiated 2-AF solutions (using dimethyl sulfoxide as a solvent) in the various tester strains indicates the rapid formation of the photo-labile 2-NOF, after which 2-NO 2F accounts for the preponderance of mutagenic activity. Continued UVA irradiation (> 72 h at 6.8 J/m 2/s) of 2-AF results in the formation of > 30 photoproducts resolvable on HPLC, several of which, in addition to 2-NOF and 2-NO 2F, are mutagenic on Salmonella but are chemically undefined to date. Prolonged irradiation ultimately destroys the photo-induced mutagenicity of 2-AF. However, UVA-induced 2-AF photoproducts are stable for several weeks when stored in sealed vials in the dark. Light potentiated oxidation of aromatic amines constitutes an alternative mechanism for the transformation of aromatic amines into proximate mutagens/carcinogens.

Electrochemical Behavior of Organic Compounds at the ( SN ) x Paste Electrode

The electrochemical characteristics of several types of organic compounds have been investigated at the paste electrode in acetonitrile/TEAP solution. The current density for reduction of benzoquinone in the presence of protons, formed either by hydroquinone oxidation or by addition of to benzoquinone, was found to be considerably less than that for this process at platinum or vitreous carbon. A similar effect was observed for proton reduction at paste, indicating, as for single‐crystal electrodes, a high hydrogen overpotential for the electrode surface. Comparative experiments investigating the redox behavior of the benzoquinone/hydroquinone system in aqueous media at paste indicate that slow protonation kinetics are involved in the voltammetric behavior observed for this system. Electrochemical oxidation of representative aromatic amines and hydrocarbons (including phenothiazine, N,N‐dimethyl‐o‐phenylenediamine, N,N‐dimethylaniline, 2,3‐diphenylindole, 2,3‐benzanthracene, and perylene) involved behavior similar to that observed at platinum, showing that the oxidized species produced, both stable and unstable, undergo no specific interaction with the electrode surface. Oxidation of pyrrole occurs at the anodic background limit of paste, producing a black film on the electrode surface which has voltammetric properties similar to those of polypyrrole films formed at other electrodes. Although the heterocyclic compounds pyridine, quinoline, and acridine are not themselves oxidizable in the paste potential range, addition of these compounds caused the appearance of an oxidation process at a potential approximately 100 mV negative of the anodic background oxidation. The dependence of the current observed for the process upon heterocycle concentration indicates that the process corresponds to a shift of the oxidation caused by a nucleophilic interaction of the heterocycles with the as it undergoes oxidation. Further negative shifts in the potential for oxidation were observed in the presence of several alkylpyridines having greater nucleophilicities than that of pyridine itself. Addition of the less nucleophilic compound thiazole did not produce this effect. These results indicate that the oxidation of itself leads to the formation of rather reactive products, while the surface behaves essentially as a noninteracting, metallic electrode in the potential region between +0.95 and −0.40V vs. SCE, over which is electrochemically stable in acetonitrile.

Bis(salicylaldehyde)ethylenedi-iminecobalt(II)-catalysed oxidation of aromatic amines with oxygen

N-n-Butylanilines undergo N-dealkylation to give a primary amine and butyraldehyde by oxidation with oxygen in the presence of bis(salicylaldehyde)ethylenedi-iminecobalt(II)(CoIIsalen) as catalyst. High conversions are obtained with high catalyst concentrations and low [substrate]/[catalyst] ratios (r). Inspection of the effect of catalyst and substrate concentrations on initial reaction rates (vin) shows poor sensitivity to the electronic effect of the nuclear substituent. Some anilines give azo derivatives at a lower rate in the same conditions.

Oxidations of aromatic amines by superoxide ion

Superoxide ion acts as a mild and highly selective oxidizing agent for aromatic amines. Aniline and α-naphthylamine were not oxidized, but β-naphthylamine formed dibenzo[a,h]phenazine, dibenzo- [a,i]phenazine and 2,2'-azonaphthalen-1-ol. o-and p-Diamines are oxidized to diaminoazobenzenes but m-diamines are unreactive. Similarly o- and p-aminophenols are oxidized to dihydroxyazo- benzenes but m-aminophenols are unaffected, and o-mercaptoaniline forms the disulfide. The oxidations are considered to be free-radical processes, initiated by hydrogen abstraction by superoxide from the substrates. The biological significance of the results is discussed.

Thermal studies on complexes of oxozirconium(IV) with some aromatic amine N-oxides

Thermal studies on complexes of oxozirconium(IV) with some aromatic amine N-oxides

Studies on ketene and its derivatives. CXIII. Reaction of dichloroketene with aromatic amine N-oxides.

Reaction of dichloroketene with pyridine 1-oxide (1) gave four products, namely, 2-dichloromethylpyridine (2), 4-dichloromethylpyridine (3), 3, 3, 7-trichloro-6-dichloroacetyl-2-oxo-2, 3, 3a, 6, 7, 7a-hexahydrofuro [2, 3-c] pyridine (4), and 3, 3-dichloro-6-dichloroacetyl-7-hydroxy-2-oxo-2, 3, 3a, 6, 7, 7a-hexahydrofuro [2, 3-c] pyridine (5). Reaction of dichloroketene with 1, followed by treatment with abs. methanol gave 3, methyl 2, 2-dichloro-2-(2-pyridyl) acetate (6), and methyl 2, 2-dichloro-2-(4-pyridyl) acetate (7). Similar reaction of dichloroketene with methylpyridine 1-oxides gave the corresponding 2-dichloro and 4-dichloro methylpyridines. On the other hand, reaction of dichloroketene with 2, 6-dimethylpyridine 1-oxide (18), followed by treatment with abs. methanol gave 4-dichloromethyl-2, 6-dimethylpyridine (19) and bis (2, 6-dimethyl-4-pyridyl) dichloromethane (21). Dichloroketene also reacted with quinoline 1-oxide (24) and isoquinoline 2-oxide (29) to give the corresponding dichloromethyl derivatives (25 and 26, and 30, respectively).

Internal reflectance spectra associated with staircase voltammetry in anodic oxidation of aromatic amines in acetonitrile

Dynamic transformation profiles of internal reflectance spectra were observed for anodic oxidation of triphenylamine, N-methyldiphenylamine, and N,N-dimethyl-aniline in acetonitrile. Absorption bands appearing in these spectra are compared with those in conventional absorption spectra of the electrolyzed aromatic amine solutions by controlled-potential electrolysis. From this comparison, the internal reflectance bands are assigned to a tetraphenylbenzidine radical monocation and dication, a dimethyl-diphenylbenzidine radical monocation and dication, etc.

Thorium(IV) and dioxouranium(VI) chelates of aromatic amine N-oxides

Thorium(IV) and dioxouranium(VI) chelates of 1,10-phenanthroline NN′-dioxide (phenO 2) and dioxouranium(VI) chelates of mono N-oxides of 2,2′-bipyridine (bipyNO) and 1,10-phenanthroline (phenNO) of the general composition ThX 4·2phenO 2 (X = Cl, Br, NO 3 or NCS); ThX 4·3phenO 2 (X = ClO 4 or I); UO 2X 2·2L (X = Cl, Br, and L = bipyNO, phenNO or phen 2); UO 2(NO 3) 2·L; UO 2X 2·3L(X = ClO 4 or I) and UO 2(NCS) 2·1.5L have been synthesised and characterized employing i.r. spectral, molar conductance, molecular weights, d.t.a. and t.g.a. data. phenO 2 acts as O,O-bidentate ligand while bipyNO and phenNO act as N,O-bidentate ligands. The coordination number of thorium in these complexes is either 6, 8 or 12; in uranium the coordination number is either 7 or 8 depending on the nature of the anions.

Cyclic Voltammetry of Aromatic Amine N-Oxides in Nonaqueous Solvents and the Stability of the Free Radicals Produced

Abstract Cyclic voltammograms of aromatic amine N-oxides were recorded in nonaqueous solvents at various sweep rates less than 10 V/s. The measurement was carried out for both cathodic and anodic sweeps, and the sweep rate for obtaining a good cyclic voltammogram was correlated with the wave height of the a.c. polarogram in the reduction and oxidation processes, respectively. A good correlation was found between the sweep rate and the wave height in both the reduction and oxidation processes. This confirmed that the two values serve as good measures of the stability of the anion or cation free radical produced by the electrode reaction of the aromatic amine N-oxides. The data were also examined by comparison with results from an electron spin resonance study. Finally, the temperature effect on the cyclic voltammogram of pyridine N-oxide was investigated in detail.