635-54-1Relevant articles and documents
Conversion of anilines into azobenzenes in acetic acid with perborate and Mo(VI): correlation of reactivities
Karunakaran,Venkataramanan
, p. 375 - 385 (2019/02/14)
Azobenzenes are extensively used to dye textiles and leather and by tuning the substituent in the ring, vivid colours are obtained. Here, we report preparation of a large number of azobenzenes in good yield from commercially available anilines using sodium perborate (SPB) and catalytic amount of Na2MoO4 under mild conditions. Glacial acetic acid is the solvent of choice and the aniline to azobenzene conversion is zero, first and first orders with respect to SPB, Na2MoO4 and aniline, respectively. Based on the kinetic orders, UV–visible spectra and cyclic voltammograms, the conversion mechanism has been suggested. The reaction rates of about 50 anilines at 20–50?°C and their energy and entropy of activation conform to the isokinetic or Exner relationship and compensation effect, respectively. However, the reaction rates, deduced by the so far adopted method, fail to comply with the Hammett correlation. The specific reaction rates of molecular anilines, obtained through a modified calculation, conform to the Hammett relationship. Thus, this work presents a convenient inexpensive non-hazardous method of preparation of a larger number of azobenzenes, and shows the requirement of modification in obtaining the true reaction rates of anilines in acetic acid and the validity of Hammett relationship in the conversion process, indicating operation of a common mechanism.
Schiff base complexes of rare earth metal ions: Synthesis, characterization and catalytic activity for the oxidation of aniline and substituted anilines
Lekha,Kanmani Raja,Rajagopal,Easwaramoorthy
, p. 72 - 80 (2014/02/14)
Several new lanthanide complexes of Pr(III), Sm(III), Gd(III), Tb(III), Er(III) and Yb(III) with the sodium salt of the Schiff base, 2-[(5-bromo-2-hydroxy-benzylidene)-amino]-5-methyl-pentanoic acid, derived from leucine and 5-bromosalicylaldehyde have been synthesized. These complexes having general formula [Ln(HL)(NO3)2(H2O)] ·NO3 were characterized by elemental analysis, UV-vis., FT-IR, EPR, Mass spectrometry and Thermal analysis. The FT-IR spectral data suggested that the ligand behaves as a tridentate ligand with one nitrogen and two oxygen donor atoms, sequence towards central metal ion. From the analytical data, the stoichiometry of the complexes was found to be 1:1 (metal:ligand). The physico-chemical data suggested eight coordination number for Ln(III) Schiff base complexes. Thermal behaviour (TGA/DTA) and fluorescence nature of the complexes were also studied. The Gd(III) Schiff base complex was found to be an efficient catalyst for the oxidation of aniline and substituted anilines under mild conditions.
Proton-coupled electron transfer in azobenzene/hydrazobenzene couples with pendant acid-base functions. Hydrogen-bonding and structural effects
Savéant, Jean-Michel,Tard, Cédric
supporting information, p. 8907 - 8910 (2014/07/08)
Electron transfer in azobenzene derivatives bearing two carboxylic acid groups is coupled with intramolecular proton transfer in a stepwise manner in the title 2e- + 2H+ redox couple. The presence of the pendant acid-base functions p
Organocatalytic oxidative dehydrogenation of aromatic amines for the preparation of azobenzenes under mild conditions
Ma, Hengchang,Li, Wenfeng,Wang, Jian,Xiao, Guanghai,Gong, Yuan,Qi, Chunxuan,Feng, Yunpeng,Li, Xiufang,Bao, Zhikang,Cao, Wei,Sun, Qiangsheng,Veaceslav, Caraus,Wang, Feng,Lei, Ziqiang
experimental part, p. 8358 - 8366 (2012/09/21)
(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.
Structure-reactivity correlation of anilines in acetic acid
Karunakaran, Chockalingam,Kamalam, Ramasamy
, p. 1118 - 1124 (2007/10/03)
The oxidation of aniline in glacial acetic acid with percarbonate, a dry carrier of hydrogen peroxide, is a second-order reaction conforming to the isokinetic relationship. The hitherto followed method of correlation of the reaction rates in terms of the structure-reactivity relationships is unsatisfactory and erroneous. But the reaction rates of molecular anilines, obtained for the first time, conform to the structure-reactivity relationships.
Mechanism and reactivity in perborate oxidation of anilines in acetic acid
Karunakaran, Chockalingam,Kamalam, Ramasamy
, p. 2011 - 2018 (2007/10/03)
Perborate but not percarbonate in acetic acid generates peracetic acid on standing and the peracetic acid oxidation of anilines is fast. The oxidation with a fresh solution of perborate in acetic acid is smooth and second order but the specific oxidation rate increases with increasing [perborate]0 or [boric acid]. Perborate on dissolution affords hydrogen peroxide and a borate; the latter assists the former in the oxidation. The oxidation rates of anilines under identical conditions do not conform to any of the linear free energy relationships but the reaction rates of molecular anilines do. Perborate oxidation proceeds via two reaction paths but the overall oxidation rates of molecular anilines conform to structure reactivity relationships; the transition states do not differ significantly. Analysis of the oxidation rates of perborate and percarbonate reveals that while perborate oxidation is faster than percarbonate it is at least as selective as the latter.
An exceptionally stable Ti superoxide radical ion: A novel heterogeneous catalyst for the direct conversion of aromatic primary amines to nitro compounds
Dewkar, Gajanan K.,Nikalje, Milind D.,Ali, Iliyas Sayyed,Paraskar, Abhimanyu S.,Jagtap,Sudalai
, p. 405 - 408 (2007/10/03)
A matrix-bound superoxide radical anion, generated by treating Ti(OR)4 (R =iPr, nBu) with H2O2, is a selective heterogeneous catalyst for the oxidation of anilines to the corresponding nitroarenes with 50 % aqueous H2O2 [Eq. (1)]. Yields of 82-98 % are obtained, even with anilines bearing electron-withdrawing substituents (R = NO2, COOH).
Lack of linear free energy relationship: Tungsten(VI) catalyzed perborate oxidation of anilines
Karunakaran,Palanisamy
, p. 571 - 575 (2007/10/03)
Operation of linear free energy relationships in tungsten(VI) catalyzed perborate oxidation was studied with 29 para-, meta- and ortho-substituted anilines. The activation parameters were calculated from k*( = rate/[substrate]2) at 35, 40, 45, 50 and 55 °C using the Erying relationship by the method of least squares. The oxidation is not isoentropic; in an isoentropic series only enthalpy of activation determines the reactivity and the isokinetic temperature is at infinity. At the isokinetic temperature all the compounds of the reaction series react at equal rate, the variation of substituent at this temperature has no influence on the free energy of activation.
Electrosynthesis and in situ chemical rearrangement of o-nitrosobenzamides
Guilbaud-Criqui, A.,Moinet, C.
, p. 101 - 110 (2007/10/02)
Primary and secondary o-nitrosobenzamides can be prepared in a "redox" cell but are unstable in the solvent used for electrolysis (acetate buffer-alcohol).At room temperature N-aryl-2-nitrosobenzamides give 2-carboxyazobenzenes.N-alkyl-2-nitrosobenzamides decompose thermally into 2-methoxy or 2-ethoxycarbonylphenylhydrazones according to the alcohol used.Similarly, methyl benzoate (or ethyl benzoate) is obtained from 2-nitrosobenzamide.A possible mechanism involves an unstable heterocycle formed by the coupling of the two nitrogen atoms (nitroso and amide) followed by cleavage of the carbonyl-nitrogen bond resulting from nucleophilic attack of the solvent (water or alcohol). Key Words: flow cell electrosynthesis / 2-nitrosobenzamides / 2-carboxyazobenzenes / 2-alkoxycarbonylphenylhydrazones / indazol-3-one
Electrochemistry of o-nitrosobenzoic acid in aqueous medium
Lamoureux, C.,Moinet, C.
, p. 599 - 603 (2007/10/02)
The electrosynthesis of 2-nitrosobenzoic acid from 2-nitrobenzoic acid, in a "redox" electrolysis cell with flowing solution through two consecutive porous working electrodes of opposite polarities, gives the monomeric form at the anode.An important part
