17277-29-1Relevant academic research and scientific papers
Conversion of anilines into azobenzenes in acetic acid with perborate and Mo(VI): correlation of reactivities
Karunakaran,Venkataramanan
, p. 375 - 385 (2019)
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.
Highly-strained cyclophanes bearing both photo- and electro-active constituents
Benniston, Andrew C.,Harriman, Anthony,Yang, Songjie,Harrington, Ross W.
, p. 5315 - 5318 (2011)
The synthesis of a highly-strained cyclophane comprising azobenzene and methyl viologen units was achieved by coupling 3,3′-dihydroxy-4,4′- bipyridine with azobenzoic acid in CH2Cl2. The molecular structure, determined by single-crystal X-ray crystallography, shows that the azobenzene NN unit adopts the trans conformation and that the bipyridinium unit is twisted. The cyclic voltammogram recorded for the target compound displays an irreversible wave at -0.37 V vs Ag/AgCl, associated with the one-electron reduction of the bipyridinium subunit. A further wave is seen at E1/2 = -1.52 V versus Ag/AgCl and is assigned to one-electron reduction of the azobenzene group. Visible light illumination of the azobenzene chromophore in CH3CN triggers trans to cis isomerization but the process is irreversible.
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.
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.
