Formation Of Azo Compounds Research Articles

A comparison of high-level theoretical methods to predict the heats of formation of azo compounds

The heats of formation (HOFs) of 57 azo compounds were calculated using six high-level theoretical models including variants of Gaussian- n (G n: G2, G2(MP2), and G3) and complete basis set (CBS- n: CBS-4M, CBS-Q, and CBS-QB3). For comparison, Hartree–Fock (HF) and density function theory (DFT) methods were also employed. The results show that the HF and DFT methods are not able to accurately predict the HOFs for the azo compounds. The G2 model presents the most accurate HOFs among the six high-level models, followed by the G2(MP2) and CBS-QB3. The CBS-Q model consistently gives more accurate HOFs than the G2 or G2(MP2) for the compounds with –NO 2. However, the case is quite the contrary for the compounds with –NH 2, –NH– or –CN. The CBS-Q or G2(MP2) model is a compromise between computation efficiency and accuracy for predicting the HOFs of the tile compounds.

Synthesis and Spectroscopic Studies on Azo-Dye Derivatives of Polymetallic Lanthanide Complexes: Using Diazotization to Link Metal Complexes Together

Heteronuclear tetrametallic lanthanide complexes have been synthesized from stable complexes by diazotization and azo-compound formation. Luminescence spectroscopy has been used to show that the complexes used as building blocks are stable under the reaction conditions.

Spectrophotometric Determination of Phenylenediamines in Different Solvents

Absorption spectra of isomeric phenylenediamines (1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine) in ten organic solvents were studied. A hypsochromic shift (toward shorter wavelengths) was observed in the spectra when the polarity of the solvent increased. Procedures for determining phenylenediamines in some solvents were developed and compared to procedures based on the formation of azo compounds.

Interaction of 1-Hydroxyethyl Radical With Glutathione, Ascorbic Acid and α-Tocopherol

Ethanol has been shown to be oxidized to a free radical metabolite, the 1-hydroxyethyl radical (HER). Interaction of HER with cellular antioxidants may contribute to the known ability of ethanol administration to lower levels of GSH and α-tocopherol. Experiments were carried out to establish a model system for the generation of HER and to study its interaction with GSH, ascorbic acid and α-tocopherol. A standard reaction for formation of azo-compounds using acetaldehyde and hydroxylamine-O-sulfonic acid was applied for the synthesis of 1,1′-dihydroxyazoethane (CH 3CH(OH)NNCH(OH)CH 3). Although stable at −70°C, thermal decomposition of this compound at room temperature was shown to produce HER, detected by EPR spectrometry as the PBN/HER or DMPO/HER spin adducts, and validated by computer simulation. GSH, present at the beginning of the experiment, inhibited formation of the PBN/HER signal. However, GSH did not cause any decay of pre-formed PBN/HER spin adduct. GSH was consumed in the presence of the HER-generating system in a reaction largely reversed by addition of NADPH plus glutathione reductase. Ascorbate also inhibited formation of the PBN/HER spin adduct and rapidly reduced the pre-formed adduct. HER amplified the oxidation of ascorbate, which was associated with the formation of the semidehydroascorbyl radical. α-Tocopherol was also consumed in the presence of HER. Production of HER in intact HepG2 cells by the redox cycling of 2,3-dimethoxy-1,4-naphthoquinone was associated with consumption of GSH. These data demonstrate the use of a simple chemical system for the controlled, continuous formation of HER and indicate that cellular antioxidants such as GSH, ascorbate, and α-tocopherol, interact with HER. The ability of agents such as ascorbate to reduce the PBN/HER spin adduct to EPR-silent product(s) may mask the quantitative detection of HER in biological systems.

ChemInform Abstract: Alkyl‐ and Fluoroalkylbenzoates of Substituted 4‐(4′‐Perfluoropropylbiphenyl‐4‐yl‐azo)phenoles.

AbstractDiazotization of 4'‐perfluoropropyl‐4‐aminobiphenyl (I), followed by coupling with the 3‐substituted phenols (II), leads to the formation of azo compounds (III) which are converted to the corresponding benzoates (V).

The base-induced decomposition of ethyl n-( [formula omitted]-azidoaryl) carbamates. An unexpected formation of azo-compounds.

A mechanistic rationale is offered to explain the formation of dihydrobenz-imidazolones and azo-compounds in the base-induced (NaH-DMF) decompositions of ethyl N-( o -azidoaryl) carbamates.

Azoverbindungen mit einem aminobicyclo[n.1.0]alkylrest

Reaction of enaminosulfonium salt 1 with different tosylhydrazides 2d,f,g leads to the formation of azo compounds 5 with an aminobicyclo[n.1.0]alkyl moiety.

Bestrahlung von 4‐allylierten 2,6‐Dimethylanilinen in Methanol

Irradiation of 4‐Allylated 2,6‐Dimethylanilines in Methanol4‐Allyl‐, 4‐(1′‐methylallyl)‐, 4‐(2′‐butenyl)‐, and 4‐(1′,1′‐dimethylallyl)‐2,6‐dimethylaniline (14–17; cf. Scheme 3) were obtained by the acid catalysed, thermal rearrangement of the corresponding N‐allylated anilines in good yields. Aniline 14, when irradiated with a high pressure mercury lamp through quartz in methanol, yielded as main product 4‐(2′‐methoxypropyl)‐2,6‐dimethylaniline (22; cf. Scheme 4) and, in addition, 2,6‐dimethyl‐4‐propylaniline (18) and 4‐cyclopropyl‐2,6‐dimethylaniline (23). The analogous products, namely erythro‐ and threo‐4‐(2′‐methoxy‐1′‐methylpropyl)‐2,6‐dimethylaniline (erythro‐ and threo‐24), 2,6‐dimethyl‐4‐(1′‐methylpropyl)aniline (19), trans‐ and cis‐2,6‐dimethyl‐4‐(2′‐methylcyclopropyl)aniline (trans‐ and cis‐25), as well as small amounts of 4‐ethyl‐2,6‐dimethylaniline (26), were formed by irradiation of 15 in methanol (cf. Scheme 5). When this photoreaction was carried out in O‐deuteriomethanol, erythro‐ and threo‐24 showed an up‐take of one deuterium atom in the side chain. The mass spectra of erythro‐ and threo‐24 revealed that in 50% of the molecules the deuterium was located at the methyl group at C(1′) and in the other 50% at the methyl group at C(2′) (cf. Scheme 6). This is a good indication that the methanol addition products arise from methanolysis of intermediate spiro[2.5]octa‐4,7‐dien‐6‐imines (cf. Scheme 7). This assumption is further supported by the photoreaction of 17 in methanol (cf. Scheme 8) which led to the formation of 4‐(2′‐methoxy‐1′,2′‐dimethylpropyl)‐2,6‐dimethylaniline (28) as main product. The occurrence of a rearranged side chain in 28 can again be explained by the intervention of a spirodienimine 31 (cf. Scheme 9). In comparison with 14, 15 and 17, the 2′‐butenylaniline 16 reacted only sluggishly on irradiation in methanol (cf. Scheme 10). It is suggested that all photoproducts ‐ except for the cyclopropyl derivatives which are formed presumably via a triplet di‐π‐methane rearrangement ‐ arise from an intramolecular singlet electron‐donor‐acceptor complex between the aniline and ethylene chromophor of the side chain. Protonation of this complex at C(3′) or C(2′) will lead to diradicals (e.g. 33 and 34, respectively, in Scheme 11). The diradicals of type 33 undergo ring closure to the corresponding spirodienimine intermediates (e.g. 31) whereas the diradicals of type 34 take up two hydrogen atoms to yield the photo‐hydrogenated compounds (e.g. 21) or undergo to a minor extent fragmentation to side chain degraded products (e.g. 30; see also footnote 7).–Irradiation of 4‐ally‐2,6‐dimethylaniline (14) in benzene or cyclohexane yielded the corresponding azo compound 38 (cf. Scheme 12), whereas its N,N‐dimethyl derivative 41 was transformed into the cyclopropyl derivative 42. The allyl moiety in 14 is not necessary for the formation of azo compounds since 2,4,6‐trimethylaniline (39) exhibited the same type of photoreaction in benzene solution.

Photochemical formation of azo-compounds from 1-phenylpyrazolones

1-Phenylpyrazolones in alcoholic media form photochemically the corresponding azo-compounds by an intermolecular reaction between the ground state of (1) and the diazonium ion (9).

Studies on the Possible Formation of Azo Compounds in Rumen Fluid

Abstract Studies of the transformations of substituted urea herbicides in rumen fluid, using metobromuron as a pilot compound, indicated that one of the products is the corresponding aniline. Because it was possible for a diazotization reaction to take place from the reduction of nitrate to hydroxylamine and ammonia through a transient nitrite step, the formation of azo compounds in rumen fluid was investigated. Incubation of 3,4-dichloroaniline with rumen fluid did not result in t he formation of any measurable azo compounds. The stability in rumen fluid of a known azo compound, 3,3’,4,4’-tetrachloroazobenzene, was also studied. Evidence is presented to show that azo compounds can break down in rumen fluid.

Pesticide transformations: production of chloroazobenzenes from chloroanilines.

Aniline and 11 different chloroanilines were added to soil. No azo compound was formed from aniline, but all monochloro-and some dichloroanilines were transformed to their corresponding dichloro-and tetrachloroazobenzenes. Other dichloroanilines and the trichloroanilines were stable in soil. Peroxidase catalyzed the formation of azo compounds by some chloroanilines. Correspondence in the range of substrates used and products formed in the two systems suggests a peroxidatic mechanism for the synthesis of azo compounds residues in soil.

Photochemistry of 2-substituted biaryls. II azo compound formation from 2-azidobiphenyl

Photochemistry of 2-substituted biaryls. II azo compound formation from 2-azidobiphenyl

Chloromethylation of Azoic Compounds. II

Insoluble azo compounds were prepared from 2-methyl-5-chloroaniline (Fast Red KB base), 2-methyl-4-chloroaniline (Fast Red TR base), 2-meteoxy -5-chloroaniline (Fast Red RC base), 4-nitroaniline (Fast Red 2G base), 2-methoxy-5-: nitroaniline (Fast Scarlet R base), and 3-nitroaniline (Fast Orange R base) as diazo components and 3-hydroxy-2-naphtho-o-anisidide (Naphtol AS-OL) and 3-hydroxy-2-naplitho-o-phenetidide (Naphtol AS-PH) as coupling components, and chloromethylation of the azo compounds has been attempted. Chloromethylat-ion of the azo compounds was possible by treating the azo cornpounds in glacial acetic acid with dry hydrogen chloride and paraformaldehyde or dichloromethyl ether, using anhydrous zinc chloride or phosphoric acid as a catalyst.Phosphoric acid was ineffective as a catalyst for formation of azo compounds from o-anisidine as a diazo comonent and 2-naphthol, 3-hydroxy-2-naphthanilide (Naphtol AS), acetoacetanilide, and 1-phenyl-3-methyl-5-pyrazolone as coupling components as reported in the first series of this report but the phosphoric acid was effective as a catalyst in the preparations of azo compounds in this report. Only one chloromethyl group was introduced in all cases and the position of its entrance was confirmed to be the para position of methoxy group in aryl ring of hydroxynaphtho-o-anisidide and para position of ethoxy group in aryl ring of hydroxymaphtho-o-phenetidide.

256. Decomposition reactions of the aromatic diazo-compounds. Part XI. The mechanism of formation of azo-compounds, polyaryls, and aryl sulphides

256. Decomposition reactions of the aromatic diazo-compounds. Part XI. The mechanism of formation of azo-compounds, polyaryls, and aryl sulphides

113. The formation of azo-compounds from o-nitrothiophenol and its methyl ether

113. The formation of azo-compounds from o-nitrothiophenol and its methyl ether