Nitrophenols substituted , complexes

The reaction course has not been elucidated (cf. also sodium hydroxide reagent). Hydrolyzation reactions and aromatizations are probably primarily responsible for the formation of colored and fluorescent derivatives. Substituted nitrophenols - e.g. the thiophosphate insecticides — can probably be hydrolyzed to yellow-colored nitro-phenolate anions by sodium hydroxide or possibly react to yield yellow Meisenheimer complexes. Naphthol derivatives with a tendency to form radicals, e.g. 2-naphthyl benzoate, react with hydrolysis to yield violet-colored mesomerically stabilized 1,2-naph-thalenediol radicals. 

A series of seven substituted BIPS were treated in toluene and ethyl acetate with phenol and with 4-nitrophenol as proton donors. The changes in absorption spectra indicated the presence of H-bonded complexes with the colored form. The equilibrium constants and thermodynamic parameters for their formation were determined. The complex formation slowed the thermal fade rate significantly.126... 

Aqueous a-cyclodextrin solutions seem to be generally applicable for TLC separation of a wide variety of substituted aromatics on polyamide thin-layer stationary sheet (13-14). In most cases, the compounds moved as distinct spots and their R, values were dependent on the concentration of the cyclodextrin in tne mobile phase. In a given family of compounds, (o-, m-, and p-nitrophenols, for example) the isomer with the largest stability constant for a-cyclodextrin complex formation had the larger value. In general, the para-substituted isomers have larger R values than the meta-isomers, which in turn have larger R values than the ortho substituted ones. 

Amines can act as reductants for excited states of other electron acceptors, too. Again, two possibilities exist (1) amine and acceptor form a CT (2) the complex formation takes place either with the excited state of the amine or with that of the electron acceptor (see discussions of ketone-amine combinations). Examples for the former principle are such combinations as DMA-nitrobenzene [105], triphenylamine-tetracyano ethylene, 4-nitrophenole, 4-aminochlorobenzene [106], tributylamine-tetrachloromethane [107], DMA-substituted chloroacetic adds [108, 109],... 

Let us call this the donor-acceptor complex proposal, similar to that presented recently for adsorption of substituted nitrobenzenes and nitrophenols on mineral surfaces [739]. The experiments on which this proposal is based are (1) isotherms of phenol, nitrobenzene, and m- and / -nitrophenol on one commercial activated carbon at pH = 2-7 and very low solute concentrations ( <1.5% of the solubility limit of these species [6]) and (2) detailed infrared (internal reflection) spectroscopic analysis of the surface after adsorption of / -nitrophenol. Interestingly, neither in this study, nor in any subsequent study that supports this mechanism, has a similar analysis been performed with carbons containing varying concentrations of carbonyl surface groups. Also of interest is that the authors dismiss the electrostatic explanation of the reported pH effects by assuming that the isoelectric point of the carbon (which was dried at 200°C for 12-24 h) was ca. 2.4. 

Murakami et al. have synthesized numerous substituted [20]- and [lO.lOJparacyclo-phanes like 70 Because of low solubility and a high tendency of aggregation, a complexation with clear stoichiometry and geometry has not been achieved. Nevertheless, a remarkable acceleration of the hydrolysis of p-nitrophenol esters has been observed, which is explained in terms of the formation of inclusion complexes between host and substrate. 

Moreno-Castilla investigated the adsorption behavior of mono-substituted phenols of different solubilities on activated carbons obtained from an original and demineralized bituminous coal. The adsorption capacity of the activated carbon was found to depend on the surface area and the porosity of the carbon, the solubility of the phenolic compound, and the hydrophobicity of the substituent. The relative affinity of the phenolic compound toward the carbon surface was related to the donor-acceptor complexes formed between the basic sites on the carbon surface and the organic ring of the phenol. The adsorption was also influenced by the pH of the solution. Marsh and Campbell observed that the adsorption of p. nitrophenol at low concentrations on polyfurfuryl alcohol and polyvinylidene chloride activated carbons was extremely sensitive to the microporous structure of these carbons and showed adsorption isotherms similar to those of nitrogen or carbon dioxide. The adsorption of p.nitrophenol was so strong at low clc values that the adsorption... 

High resolution carbon-13 NMR spectroscopy is one of the most useful methods in the analysis of the structure and molecular dynamics of cyclodextrin inelusion-complexes both in aqueous solution[1,2] and in the solid state[3]. Earlier cariDon-13 NMR studies of a-CD inclusion complexes with benzoic acid, p-nitrophenol, and p-nitrophenolate in aqueous solution have shown that the included lead(head see Fig.lA) carbons show high-field shifts compared to low-field shifts of corresponding para(tail Fig.lA) carbons[4,5]. Similar distinctive patterns of carbon-13 displacement s have been also observed for p-hydroxybenzoic acid and it has been concluded that the carboxyl group of p-hydroxybenzoic acid is directed into the a-CD cavity [4]. A variety of substituted benzenes are known to show quite similar carbon-13 high (head) and low (tail) field shifts, irrespective of the kinds of substituents if their size are matched to the a-CD cavity [4,5]. These characteristic carbon-13 displacements induced by complexation with a-CD... 

In a previous report [7], we have successfully applied the quantum chemical method to the determination of the geometry of a-CD inclusion-complexes with substituted benzenes such as p-nitrophenol, p-hydroxy-benzoic acid, and benzoic acid. This method was based on the so-called solvent-effect theory and it was assumed that the a-CD cavity has the environmental effect of lower dielectric constant( l) on a included part of the guest and the other part of guest is exposed to the aqueous phase of higher dielectric constant( 2) shown in Fig,IB. 

The use of chitosan-Pd nanocomposites for heterogeneous catalytic reactions is the most extensively studied system and reported in the literature. For example, aUylic substitution reactions of ( )-cinnamyl ethyl carbonate by morpholine was reported by Quignard et al. (2000) using a chitosan-supported palladium complex. Dechlorination reaction of chlorophenol to phenol, degradation of nitrophenol, and reduction of chromate were studied by Vincent et al. (2002, 2003, 2004). Hydrogenation of nitrobenzene to aniline by chitosan-impregnated palladium composites was also reported by Jin et al. (1994). Excellent review of chitosan-based materials used in the heterogeneous catalytic reactions... 

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