3646-57-9Relevant articles and documents
Electrochemically initiated transformation of 4-nitrophenylhydroxylamine into 4,4′-dinitroazobenzene
Syroeshkin, Mikhail A.,Mikhalchenko, Ludmila V.,Leonova, Marina Yu.,Mendkovich, Andrei S.,Rusakov, Alexander I.,Gul'Tyai, Vadim P.
, p. 26 - 28 (2011)
Based on controlled potential electrolysis and cyclic voltammetry, the chain reaction of 4,4′-dinitroazobenzene formation was shown to be initiated during the electrochemical reduction of 4-nitrophenylhydroxylamine in DMF.
Correlation studies in the oxidation of Vanillin Schiff bases by acid bromate - A kinetic and semi-empirical approach
Sathish,Teja, P. Ravi,Ramudu, M. Parusha,Manjari, P. Sunitha,Rao, R. Koteshwar
, (2021/12/13)
Kinetics and mechanistic aspects of oxidation of Vanillin Schiff bases (obtained from Vanillin and p-substituted anilines) by bromate in acid medium has been studied at 313 ?K. The reaction exhibited first order in [bromate] and less than unity order each in [Vanillin Schiff base] and [acid]. The increase in the rate of reaction with decrease in dielectric constant of the medium is observed with all the studied substrates. The reaction failed to induce the polymerization of acrylonitrile. Electron withdrawing substituents in the aniline ring moiety of Vanillin Schiff base accelerate the rate of oxidation to a large extent and electron releasing substituents retard the rate. The order of reactivity is found to be p-nitro ?> ?p-bromo ?> ?p-chloro ?> ?–H ?> ?p-fluoro ?> ?p-methyl ?> ?p-methoxy ?> ?p-ethoxy and the sensitivity of the substrates towards the reaction rate is further supported by the semi-empirical calculation of electronic properties and global descriptors of the substrates (Vanillin Schiff bases) with different substituents in the aniline ring moiety. The observed trend in the reactivity of the substrates was correlated with the calculated descriptors like electronegativity, chemical potential, electrophilicity index, chemical hardness and frontier molecular orbitals. The linear free-energy relationship is characterized by a straight line in the Hammett's plot of log k versus σ. The ρ values are positive and increase with increase in temperature. From the Exner and Arrhenius plots, the isokinetic relationship is discussed. Oxidation products identified are p-substituted azobenzene and vanillic acid. Based on the experimental observations, a plausible mechanism is proposed and rate law is derived.
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.
Rh(III)-catalyzed [4?+?1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides toward 3-acyl-(2H)-indazoles
Zhu, Jiawei,Sun, Song,Cheng, Jiang
supporting information, p. 2284 - 2287 (2018/05/23)
A Rh(III)-catalyzed [4 + 1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides was developed to access 2H-indazoles in moderate to excellent yields with good functional group compatibilities. It proceeded with the sequential insertion of the Rh(III) carbene to the C?H bond and cyclization steps, where sulfoxonium ylides served as efficient and stable carbene precursor.
