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Functionalization of Graphite and Graphene
Published in Titash Mondal, Anil K. Bhowmick, Graphene-Rubber Nanocomposites, 2023
Akash Ghosh, Simran Sharma, Anil K. Bhowmick, Titash Mondal
Diazonium chemistry has a significant contribution in the covalent functionalization of material. It emphasizes the carbon-carbon bond formation using diazonium salt for the tuning of graphitic-like materials—the functionalization reaction is believed to be governed by the free radical mechanism. The generic functionalization of graphene via the diazonium chemistry is shown in Figure 4.4. Liu et al. reported that aniline was functionalized on graphene nanosheet using diazonium coupling, further reduced by hydrazine. The functional attachment was confirmed by X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectroscopy, and Raman Spectroscopy. The diazonium salt releases a molecule of nitrogen gas and produces a highly reactive aryl radical using any thermal, photochemical, or electrochemical stimuli. As the radical gets covalently attached with the graphitic material, the hybridization of graphitic carbon changes from sp2 to sp3. Consequently, the aromatic system will get disrupted, and a change is observed in the electronic behavior (Liu et al. 2014).
Advances in Industrial Wastewater Treatment
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
These side groups are necessary to obtain colors with different shades and intensities. Azo dyes go to the shade of greenish yellow to orange, red, purple, and brown. The colors depend largely on the chemical structure, whereas the different shades depend more on physical properties. However, the disadvantage, which limits their commercial application, is that most of them are reds and none are green. The synthesis of most of the azo dyes involves diazotizing a primary aromatic amine to give a diazonium salt. The diazonium compound is then coupled with one or more nucleophilic agents. The amino and hydroxyl groups are the only coupling agents used. The coupling reaction is generally in para position with respect to the amino group or to the hydroxyl groups (Fu and Viraraghavan 2001). The general regime of dye azo synthesis is illustrated in Figure 3.6.
Derivatization Reactions in Trace Chemical Analysis
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
Substances may be diazotized to produce their diazonium salts which are then combined with coupling reagents to form colored azo dyes for their determination by spectrophotometry. The products usually have intense and characteristic colors. In such diazotization reactions, the nitrite anion (NO2−) is converted into an azo intermediate (tetravalent N with a positive charge on it). An example is the reaction of nitrite ion with sulfanilamide to produce a diazonium salt which is then reacted with N-(1-naphthyl)ethylenediamine to form an intense colored azo derivative. This is an example of a typical colorimetric test involving diazotization and coupling reactions. The reaction steps are presented in Chapter 39. The same test may be applied to measure nitrate, however after reducing the nitrate ion into nitrite, which is then subjected to diazotization and coupling. The reduction of nitrate to nitrite may be carried out effectively using cadmium or SnCl2 or any other suitable reducing agent.
Transition metal complexes incorporating lawsone: a review
Published in Journal of Coordination Chemistry, 2022
Freeda Selva Sheela Selvaraj, Michael Samuel, Arunsunai Kumar Karuppiah, Natarajan Raman
Gokhale et al. reported complexes with lawsone coupled with diazonium salt at C-3 position (11). The diazonium salt is prepared by treating a toluidine derivative with sodium nitrite and HCl. Lawsone dissolved in ethanol is coupled with the diazonium salt in the presence of excess sodium acetate below 10 °C. The obtained orange-red precipitate was filtered, washed with cold water and ethanol and dried in vacuum. To synthesize the copper complexes, the methanolic solution of the ligand was treated with metal salt in the ratio 2:1 under reflux for 3 h. The obtained precipitate was filtered, washed with ethanol and dried in vacuum [51]. The complex prepared has square planar geometry with intermolecular stackings. A similar complex (12) has been prepared by Francisco et al. using the same procedure [52].
Chromium (III) complexes of azo dye ligands: Synthesis, characterization, DNA binding and application studies
Published in Inorganic and Nano-Metal Chemistry, 2018
Nasir Abbas, Syed Ahmad Tirmizi, Ghulam Shabir, Aamer Saeed, Ghulam Hussain, Pervaiz Ali Channer, Rashid Saleem, Muhammad Ayaz
Azo compounds are very important molecules and have attracted much attention in both academic and applied research.[10] Most azo dyes are prepared from Diazonium salts furthermore they constitute 60–70% of the industrial dyes used today. The obtained chromium complexed azo dyes are colored and have been widely used in many practical applications such as printing systems, coloring fibers, photo-electronic applications, optical storage technology as well as biological reactions[1] and analytical chemistry.[15] Also the importance of heterocyclic azo dyes and their metal complexes may stem from their biological activity.[5] Metal complexes of azo dyes ligand have extensive applications in electro-photographic toners as charge controlling[4] agents, developers in power coating materials and in electrostatic separation process.[7] Azo derivatives and their complexes are very important pigments for synthetic leather and vinyl polymers.[10] Many azo dyes have been utilized as chromogenic reagents for colorimetric determinations and as indicators for complexometric titrations.[13] The azo metal complexes were applied on leather and their color fastness studies were performed.
Synthesis of arylazothiazole dyes in the presence of sulfonated nanostructures
Published in Journal of Sulfur Chemistry, 2020
Simin Mollaei, Zohre Zarnegar, Javad Safari
In recent years, the synthesis of 2-amino-5-arylazothiazole dyes has been carried out in the presence of liquid mineral acids. However, many disadvantages have limited the applications of these acids in the formation of diazonium salts and azo coupling such as strong corrosiveness in high acidic conditions, costly and inefficient separation from homogeneous reaction environments, and creation of a large amount of waste by-products. We tried to solve these problems by developing an environmentally friendly and simple approach for the synthesis of arylazothiazole dyes using SO3H heterogeneous catalysts.