Formation Of Azo Compounds Research Articles

Graphite-Catalyzed Electro-Oxidation of Hydrazine Derivatives Using Sodium Chloride under Green and Sustainable Chemistry

The development of efficient and environmentally friendly catalysts for the electro-oxidation of hydrazine derivatives is of great importance in various industrial applications. In this study, we report the utilization of graphite-based catalysts for the electro-oxidation of hydrazine derivatives, using sodium chloride as a green and sustainable chemical approach. Graphite, a two-dimensional carbon material with exceptional properties, offers numerous advantages as a catalyst, including its high surface area, excellent electrical conductivity, and chemical stability. These characteristics make graphite an ideal candidate for promoting electrochemical reactions. Sodium chloride (NaCl), a readily available and cost-effective salt, serves as a green alternative to traditional oxidants used in hydrazine oxidation processes. By replacing conventional oxidizing agents with NaCl, we aim to reduce the environmental impact associated with the production and disposal of hazardous chemicals. This process enables the transformation of the HN-NH bond within hydrazines, leading to the formation of azo compounds (N = N). Azo compounds are important organic molecules with diverse applications in organic synthesis. This novel approach has successfully showcased the efficacy of utilizing various azo compounds in 13 different examples, yielding excellent or moderate to good results. The method capitalizes on electricity as the final oxidizing agent, providing an environmentally friendly oxidation strategy. Its high efficiency and gentle reaction conditions make this technique valuable for synthesizing azo derivatives, even when working with hydrazines containing diverse functional groups, resulting in yields ranging from moderate to excellent. Through systematic experiments, we evaluated the catalytic performance of graphite-based catalysts in the electro-oxidation of hydrazine derivatives. The catalysts demonstrated remarkable catalytic activity due to their efficient conversion of hydrazine derivatives into desired products. Moreover, the system exhibited good stability and recyclability, suggesting its suitability for practical applications.

Digital image colorimetric detection of ceftazidime based on azo compound formation on a polyethyleneimine-modified cotton sponge.

A novel colorimetric platform using cotton sponges modified with polyethyleneimine (PEI) was fabricated for the detection of ceftazidime through the diazotization and coupling reaction. In this work, cotton sponges were initially prepared by freeze drying using 2 w/w% cotton fibers modified with 3-aminopropyl triethoxysilane (APTES), followed by grafting of PEI through a crosslinking reaction using epichlorohydrin (ECH). The optimal concentrations of modifying agents were 170 mM APTES for 1.0 g of cotton fibers and 210 μM PEI for 0.5 g of APTES sponges. With a sample volume of 150 mL, the extracted ceftazidime was detected through the reactions with 0.5 M HCl, 30 mM NaNO2, and 25 μM chromotropic acid on the sponge surface. The PEI-sponge platform provided good selectivity and sensitivity for ceftazidime determination within 30 min. The linear working range for ceftazidime determination was in the range of 0.5-3.0 mg L-1 with a limit of detection (LOD) of 0.06 mg L-1. The proposed method was successfully applied to detect ceftazidime in water samples with satisfactory recovery (83-103%) and reproducibility (<4.76% RSD).

Determination of the optimum concentration of the coupling agent in chloramphenicol analysis

The aim of this research is to determine the optimum concentration of the coupling agent used in chloramphenicol analysis, then calculate the limit of detection of that photometric reaction. Chloramphenicol is a colorless compound that is often abused in animals whose products are consumed by humans. Chloramphenicol has side effects on the human body. So, chloramphenicol must be analyzed. To facilitate the analysis process, chloramphenicol must be converted into colored compounds called azo compounds. To make azo compounds must go through the process of reduction, diazotization, and coupling. A coupling agent is an important compound that played a role in an azo compound formation and was analyzed using UV-Vis spectrophotometer. This research, used N-(-1-Naphthyl) ethylenediamine dihydrochloride (NEDA) with variations concentrations of 0.1%, 0.3%, 0.5% at 565 nm. The optimum coupling concentration that gives maximum absorbance was 0.1%. The detection limit (LOD) obtained by using the optimum coupling is 0.0498 μg/mL, the limit of quantitation (LOQ) is 0.1660 μg/mL, the sensitivity value is 0.1425, and a correlation coefficient (R2) of 0.999 with a concentration range of chloramphenicol is 0,14 - 1,4 ppm.

Hydrogenation of nitroarenes on silica-supported copper catalyst

A 9% Cu/SiO2 catalyst prepared by the deposition– precipitation technique was active in the hydrogenation of substituted nitrobenzenes at 170 °C and 13 atm H2 in a batch reactor. Nitro groups were selectively reduced to NH2 groups except for the case of 5-bromo-1,3-dinitrobenzene. The selectivity of the overall process is somewhat suppressed by inevitable formation of azo compounds and traces of tars due to the reactions of the obtained amines with nitroso intermediates.

Azo synthesis meets molecular iodine catalysis.

A metal-free synthetic protocol for azo compound formation by the direct oxidation of hydrazine HN–NH bonds to azo group functionality catalyzed by molecular iodine is disclosed. The strengths of this reactivity include rapid reaction times, low catalyst loadings, use of ambient dioxygen as a stoichiometric oxidant, and ease of experimental set-up and azo product isolation. Mechanistic studies and density functional theory computations offering insight into this reactivity, as well as the events leading to azo group formation are presented. Collectively, this study expands the potential of main-group element iodine as an inexpensive catalyst, while delivering a useful transformation for forming azo compounds.

Azobindungsbildung auf Metalloberflächen

AbstractDie Bildung von Azoverbindungen durch Redoxkreuzkupplung von Nitroarenen und Arylaminen, welche in Lösungsmittelchemie herausfordernd ist, wird durch Oberflächenchemie ermöglicht. Die Reaktionsprodukte werden mit einem kryogenen Rastertunnelmikroskop (STM) und per Röntgenphotoelektronenspektroskopie (XPS) analysiert. Durch die Verwendung gut konzipierter Vorläufer, welche eine Amino‐ und eine Nitrofunktion enthalten, werden Azopolymere durch hocheffiziente Nitro‐Amino‐Kreuzkupplung auf der Oberfläche hergestellt. Experimente mit anderen Substraten und Oberflächenorientierungen zeigen, dass die Metalloberfläche einen signifikanten Einfluss auf die Reaktionseffizienz hat. Zudem wurde herausgefunden, dass die Reaktion partiell oxidierter/reduzierter Vorläuferverbindungen in Dimerisierungsreaktionen ebenfalls stattfindet, was Licht auf den Mechanismus wirft, welcher durch DFT‐Berechnungen weiter untersucht wurde.

Azo bond formation on metal surfaces.

The formation of azo compounds via redox cross‐coupling of nitroarenes and arylamines, challenging in solution phase chemistry, is achieved by on‐surface chemistry. Reaction products are analyzed with a cryogenic scanning tunneling microscope (STM) and X‐ray photoelectron spectroscopy (XPS). By using well‐designed precursors containing both an amino and a nitro functionality, azo polymers are prepared on surface via highly efficient nitro‐amino cross‐coupling. Experiments conducted on other substrates and surface orientations reveal that the metal surface has a significant effect on the reaction efficiency. The reaction was further found to proceed from partially oxidized/reduced precursors in dimerization reactions, shedding light on the mechanism that was studied by DFT calculations.

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene.

Photolysis is one of the main transformation pathways for 2,4,6-trinitrotoluene (TNT) released into the environment. Upon exposure to sunlight, TNT is known to undergo both oxidation and reduction reactions with release of nitrite, nitrate, and ammonium ions, followed by condensation reactions of the oxidation and reduction products. In this study, compound classes of transformation products from the aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene (TNT) have been identified by liquid and solid state 13C and 15N NMR. Aqueous phase experiments were performed on saturated solutions of T15NT in deionized water, natural pond water (pH = 8.3, DOC = 3.0 mg/L), pH 8.0 buffer solution, and in the presence of Suwannee River Natural Organic Matter (SRNOM; pH = 3.7), using a Pyrex-filtered medium pressure mercury lamp. Natural sunlight irradiations were performed on TNT in the solid phase and dissolved in the pond water. In deionized water, carboxylic acid, aldehyde, aromatic amine, primary amide, azoxy, nitrosophenol, and azo compounds were formed. 15N NMR spectra exhibited major peaks centered at 128 to 138 ppm, which are in the range of phenylhydroxylamine and secondary amide nitrogens. The secondary amides are proposed to represent benzanilides, which would arise from photochemical rearrangement of nitrones formed from the condensation of benzaldehyde and phenylhydroxylamine derivatives of TNT. The same compound classes were formed from sunlight irradiation of TNT in the solid phase. Whereas carboxylic acids, aldehydes, aromatic amines, phenylhydroxylamines, and amides were also formed from irradiation of TNT in pond water and in pH 8 buffer solution, azoxy and azo compound formation was inhibited. Solid state 15N NMR spectra of photolysates from the lamp irradiation of unlabeled 2,6-dinitrotoluene in deionized water also demonstrated the formation of aromatic amine, phenylhydroxylamine/ 2° amide, azoxy, and azo nitrogens.

Metal-Catalysed Azidation of Organic Molecules.

The azide moiety is a desirable functionality in organic molecules, useful in a variety of transformations such as olefin aziridination, C–H bond amination, isocyanate synthesis, the Staudinger reaction and the formation of azo compounds. To harness the versatility of the azide functionality fully it is important that these compounds be easy to prepare, in a clean and cost‐effective manner. Conventional (non‐catalysed) methods to synthesise azides generally require quite harsh reaction conditions that are often not tolerant of functional groups. In the last decade, several metal‐catalysed azidations have been developed in attempts to circumvent this problem. These methods are generally faster, cleaner and more functional‐group‐tolerant than conventional methods to prepare azides, and can sometimes even be conveniently combined with one‐pot follow‐up transformations of the installed azide moiety. This review highlights metal‐catalysed approaches to azide synthesis, with a focus on the substrate scopes and mechanisms, as well as on advantages and disadvantages of the methods. Overall, metal‐catalysed azidation reactions provide shorter routes to a variety of potentially useful organic molecules containing the azide moiety.

A Laser Flash Photolysis Study of Azo-Compound Formation from Aryl Nitrenes at Room Temperature.

The species 4-nitrenopyridine 1-oxide is known to exhibit triplet nitrene dominated chemistry to yield azo-dimer products exclusively, even at room temperature. As such, this species, and its analogue 4-nitrenoquinoline 1-oxide, are useful models to probe the mechanism of formation of azo-dimers, which is postulated to proceed by self-reaction of the nitrene or reaction of nitrene with the parent azide. A laser flash photolysis study is described where the kinetics of formation of azo-dimer were found to be most adequately modeled by competition between both mechanisms, and rate coefficients for the competing reactions were determined.

Reversible coupling of 4-nitroaniline molecules to 4-aminothiophenol functionalized on Ag nanoparticle/graphene oxide nanocomposites through the plasmon assisted chemical reaction

In this study, we demonstrate the formation of azo compounds on a composite of silver nanoparticles and graphene oxides (Ag@G) through a plasmon-assisted coupling reaction between different amine compounds.

ChemInform Abstract: Palladium‐Catalyzed Direct Regioselective ortho‐Phosphonation of Aromatic Azo Compounds with Dialkyl Phosphites.

An efficient palladium-catalyzed regioselective C–P bond formation of azo compounds through C–H bond functionalization using dialkyl phosphites as phosphorus source under mild conditions was developed. A series of both symmetrical and unsymmetrical azoarenes were successfully phosphonylated through this procedure with tolerance of a broad range of functional groups.

Exclusive formation of azo-compounds upon hydrogenolysis of nitrobenzeneseleninic acid derivatives over Pd/C

Hydrogenolysis of 3-nitrobenzeneseleninic acid and 3-bromo-4-nitrobenzeneseleninic acid under standard conditions (Pd/C, H2 1 atm in MeOH) gave exclusively the corresponding azo-compounds. Nitration of the azo-compounds with HNO3 in H2SO4 at 0 °C yielded solely 3-nitrobenzeneseleninic acid and 3-bromo-4-nitrobenzeneseleninic acid in return.

Reactions of N-alkylhydrazones of aliphatic ketones

For the first time data concerning the reactions of N-alkylhydrazones of aliphatic ketones have been systematized. The possible reaction centres of hydrazones and the main lines of attack for electrophilic and nucleophilic reagents have been distinguished. Differences in the reactivity of N-alkyl and N-arylhydrazones have been studied. The types of tautomerism of hydrazones and their impact on the reactivity of these compounds have been considered. Most reactions occurring on the sp2-hybridized carbon atom lead to formation of azocompounds, which are generally aliphatic radical sources or initiators of radical processes. The interaction of hydrazones with oxidising reagents leading to the corresponding bisazocompounds has been studied. For a number of N-acylation hydrazones the ring-chain tautomerism has been described, as a result these compounds exist in cyclic and acyclic forms. The general methods for construction of heterocyclic compounds based on N-alkylhydrazones of aliphatic ketones due to cyclization of hydrazones with bis-functional reagents on both nitrogen atoms, as well as the nitrogen atom and the carbon atom have been considered. Hydrazone-enhyidrazine tautomerism is inherent to hydrazones of aliphatic ketones with the α-methylene group; it causes a simultaneous attack of dielectrophiles on the sp3-hybridized carbon atom and the nitrogen atom of hydrazone and can be used to construct derivatives of pyridazine and pyrazole, and the use of compounds of phosphorus and of silicon as dielectrophiles results in formation of phosphodiazoles and silapyrazolines, respectively. Reduction reactions for C=N bond of N-alkylhydrazones of aliphatic ketones have been studied.

Palladium-catalyzed direct regioselective ortho-phosphonation of aromatic azo compounds with dialkyl phosphites.

An efficient palladium-catalyzed regioselective C-P bond formation of azo compounds through C-H bond functionalization using dialkyl phosphites as phosphorus source under mild conditions was developed. A series of both symmetrical and unsymmetrical azoarenes were successfully phosphonylated through this procedure with tolerance of a broad range of functional groups.

ChemInform Abstract: Rhodium‐Catalyzed Direct ortho C—N Bond Formation of Aromatic Azo Compounds with Azides.

An efficient rhodium-catalyzed regioselective C–N bond formation of azo compounds in good to excellent yields through C–H bond functionalization using azides as the nitrogen source was developed. Alkyl, aryl, and sulfonyl azides could be efficiently assembled in this reaction with excellent functional group tolerance.

Rhodium-Catalyzed DirectorthoC–N Bond Formation of Aromatic Azo Compounds with Azides

An efficient rhodium-catalyzed regioselective C-N bond formation of azo compounds in good to excellent yields through C-H bond functionalization using azides as the nitrogen source was developed. Alkyl, aryl, and sulfonyl azides could be efficiently assembled in this reaction with excellent functional group tolerance.

Photocatalytic reduction of nitroarenes to azo compounds over N-doped TiO2: relationship between catalysts and chemical reactivity

This work deals with selective reduction of aromatic nitro compounds to corresponding symmetrical substituted azo compounds using nitrogen-doped TiO2 nanoparticles as photocatalyst in the presence of a catalytic amount of formic acid. Various azo compounds containing additional reducible substituents including halogens, and carboxyl and phenol functions have been synthesized in a single step by use of this catalyst. The conversion was reasonably fast, clean, and high yielding at room temperature. A mechanism of formation for the azo compounds is proposed. The behavior of the N/TiO2 catalyst is of particular interest because this is the first time, as far as we know, that formation of azo compounds has been catalyzed by an N-doped TiO2 photocatalyst. Nitrogen-doped TiO2 was prepared by a simple modified sol–gel process with urea as nitrogen source. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy, and transmission electron microscopy. The chemical nature of N was identified by XPS as N–Ti–O in the anatase TiO2 lattice.

Organocatalytic oxidative dehydrogenation of aromatic amines for the preparation of azobenzenes under mild conditions

(Diacetoxyiodo)benzene used as stoichiometrically and catalytically in the preparation of azobenzenes under mild reaction conditions was developed. The metal-free oxidation systems demonstrated wide substituents tolerance, alkyls, halogens, and several versatile functional groups, such as amino, ethynyl, and carboxyl substituents are compatible well, and the corresponding products could be formed with good to excellent yields. In this disclosed method, the more large scale formation of azo compounds also could be carried out successfully. Of note that 3-ethynylbenzenamine applied as a very useful cross dehydrogenative partner, which coupled with different anilines, providing asymmetrical azo compounds with acceptable yields in one step under very mild reaction conditions.

Simultaneous stepwise injection-photometric determination of nitrite and nitrate ions in aqueous media

A procedure for the stepwise injection-photometric determination of nitrite and nitrate ions has been developed. The procedure employs their subsequent determination by the reaction of colored azo compound formation after the reduction of nitrate ions into nitrite ions on a cadmium reducer. The analytical ranges for nitrite and nitrate ions are 2–15 and 5–50 mg/L (sample volume 2 mL, analysis time 14 min).