scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Selective solvation of hydrophobic ions in structured solvents. Azo-hydrazone tautomerism of azo dyes in aqueous organic solvents

01 Nov 1970-Journal of Organic Chemistry (American Chemical Society)-Vol. 35, Iss: 11, pp 3670-3675
About: This article is published in Journal of Organic Chemistry.The article was published on 1970-11-01. It has received 78 citations till now. The article focuses on the topics: Solvation & Tautomer.
Citations
More filters
Journal ArticleDOI
TL;DR: Two types of interactions involving low-valent metal compounds have been observed: methylene arenium complexes which result from positive charge transfer to the aromatic ring and sigma-bonded C-H and C-C agostic complexes of cationic metals.
Abstract: This Account presents an overview of current research activities that focus on novel types of interactions between cationic transition metal complexes and arene systems and on unprecedented quinonoid complexes which result from such interactions. When a negatively charged phenoxy group is present in a position para to the metal in a high oxidation state, intramolecular charge transfer occurs, giving the corresponding metallaquinones or quinone methide complexes. In addition, two types of interactions involving low-valent metal compounds have been observed: methylene arenium complexes which result from positive charge transfer to the aromatic ring and σ-bonded C−H and C−C agostic complexes of cationic metals. These σ-complexes are proposed as intermediates in metal-based bond activation processes.

129 citations

Journal ArticleDOI
TL;DR: The phenomenon of azo-hydrazone tautomerism of hydroxyazo compounds is reviewed in this article in relation to structural factors such as the degree of annellation and the type and position of substituents.

122 citations

Journal ArticleDOI
Ho Yong Lee1, Xinli Song1, Hyunsoo Park1, Mu-Hyun Baik1, Dongwhan Lee1 
TL;DR: These findings implicate that the hydrogen-bonding donor ability is a key requirement for the binding-induced conformational switching, which allows for direct naked-eye detection of volatile amines under ambient conditions.
Abstract: An efficient triple azo coupling reaction between anilines and phloroglucinol furnished a series of C3-symmetric molecules 7−9 supporting multiple conjugation pathways that converge at the molecular core. A combination of 1H/13C NMR spectroscopy, X-ray crystallography, and density functional theory computational studies provided a coherent picture of the [n,π]-conjugated molecular core, which is best described as the tris(hydrazone) [rather than tris(azo)] tautomer stabilized by resonance-assisted hydrogen bonding. For a homologous series of compounds, an increase in the torsional angles between the planar molecular core and the peripheral aryl groups results in a systematic blue shift in the low-energy electronic transitions (7, 523 nm; 8, 505 nm; 9, 445 nm in CHCl3) that qualitatively correlates with the shrinkage of effective conjugation through structural distortion. Similar spectral shifts could also be induced by amine substrates that interact with the intramolecular hydrogen-bonding network to trig...

101 citations

Journal ArticleDOI
15 Jun 2012
TL;DR: A comparison between the absorbance spectra of the dyes in micellar solution with spectra in a range of solvents of different polarity indicated that the dye is situated in a relatively polar environment, and it is assumed that the dyed is located just below the head group region of the micelle.
Abstract: Solubilization of two different types of organic dyes, Quinizarin with an anthraquinone structure and Sudan I with an azo structure, has been studied in aqueous solutions of a series of cationic gemini surfactants and of a conventional monomeric cationic surfactant, dodecyltrimethylammonium bromide (DTAB). Surfactant concentrations both above and below the critical micelle concentration were used. The concentration of solubilized dye at equilibrium was determined from the absorbance of the solution at lambda(max) with the aid of a calibration curve. The solubilization power of the gemini surfactants was higher than that of DTAB and increased with increasing alkyl chain length. An increase in length of the spacer unit resulted in increased solubilization power while a hydroxyl group in the spacer did not have much effect. Ester bonds in the alkyl chains reduced the solubilization power with respect to both dyes. A comparison between the absorbance spectra of the dyes in micellar solution with spectra in a range of solvents of different polarity indicated that the dye is situated in a relatively polar environment. One may therefore assume that the dye is located just below the head group region of the micelle. Attractive it-cation interactions may play a role for orienting the dye to the outer region of the micelle.

94 citations

Journal ArticleDOI
TL;DR: Calculated structures of the three hydrazone models are similar to each other and that of the model without a sulfonate group closely matches its reported crystal structure, and the EPR spectrum obtained on one-electron reduction of Orange II by the 2-hydroxy-2-propyl radical (*CMe2OH) is attributed to the hydrazyl radical produced on protonation of the radical anion.
Abstract: The structure and bonding of the azo dye Orange II (Acid Orange 7) in parent and reduced forms have been studied using NMR, infrared, Raman, UV−visible, and electron paramagnetic resonance (EPR) spectroscopy, allied with density functional theory (DFT) calculations on three hydrazone models (no sulfonate, anionic sulfonate, and protonated sulfonate) and one azo model (protonated sulfonate). The calculated structures of the three hydrazone models are similar to each other and that of the model without a sulfonate group (Solvent Yellow 14) closely matches its reported crystal structure. The 1H and 13C NMR resonances of Orange II, assigned directly from 1D and 2D experimental data, indicate that it is present as ≥95% hydrazone in aqueous solution, and as a ca. 70:30 hydrazone:azo mixture in dimethyl sulfoxide at 300 K. Overall, the experimental data from Orange II are matched well by calculations on the hydrazone model with a protonated sulfonate group; the IR, Raman, and UV−visible spectra of Orange II are ...

70 citations