Quinones types

Dyes, quinone type used for anthraquinones, indamines, indoarulines, indophenols, and miscellaneous quinones (see Dyes, anthraquinone). 

Coelenterazine (A) is oxidized into dehydrocoelenterazine (D) by MnC>2 in a mixed solvent of ethanol and ether (Inoue et al., 1977b). Dehydrocoelenterazine (C26H19O3N3) can be obtained as dark red crystals. It does not have the capability of chemiluminescence. The ultraviolet absorption spectrum (Fig. 5.6) shows its absorption maxima at 425 nm (e 24,400) and 536 nm (g 12,600) in ethanol. An addition of NaOH significantly increases the 536 nm peak at the expense of the 425 nm peak. Dehydrocoelenterazine can take a tautomeric structure of quinone type (not shown), in which the phenolic proton on the 2-substituent is shifted onto the N(7) of the imida-zopyrazinone ring. Dehydrocoelenterazine can be readily reduced to... 

An important problem encountered with polymer electrodes is that of overoxidation. It occurs after reversible charging of the electrode at high oxidation potentials and leads to polymer degeneration. The results of thorough studies show that such degenerative mechanisms are promoted by the nucleophilicity of the solvent. Especially the activity of water leads to the formation of quinone-type compounds, to the cleavage of C—C bonds, the liberation of CO2, and the formation of carboxylic acids Hence, there is a clear tendency to avoid both nucleophile solvents... 

Quinones, lipid-soluble substances involved in electron transport, can also be used as biomarkers. Lipski et al. (155) u.sed quinone analyses, physiological tests, and fatty acid profiles to differentiate Gram-negative non-fermentative bacteria isolated from biofilters. Quinone type was found to be an efficient method to group isolates prior to the analysis of results from the physiological tests. The detection of quinones appears to be restricted to the discrimination of isolated colonies and has limited potential to the analysis of mixed populations. 

Soares GMB, Costa-Ferreira M, Pessoa de Amorim MT (2001) Decolorization of an anthra-quinone type dye using a laccase formulation. Bioresour Technol 79 171... 

Some metabolites, most commonly aromatic hydroxylamines and quinone-type metabolites, can undergo redox cycling and generate reactive oxygen species, especially... 

Isaacson and Sawhney (60) studied the reactions of a number of phenols and smectite with transition metal (Cu, FeJ+) and nontransition metal exchangeable cations. IR spectra of the clay-phenol complexes showed that all the clays studied transformed the sorbed phenols. The transformation occurred to a much greater extent in clays with transition metal cations than in those with the non-transition metal cations. In a subsequent study, Sawhney et al. (61) studied the polymerization of 2,6-dimethylphenol on air-dried homoionic Na-, Ca-, A1-, and Fe-smectite at 50°C. A portion of the adsorbed 2,6-dimethylphenol was transformed into dimers, trimers, tetramers, and quinone-type compounds. The nature of the exchange cations had an effect on both sorption and transformation and decreased in the order Fe Al > Ca > Na. 

One company which purchases 3,3 -dichlorobenzidine as the dihydrochloride salt in sealed fiber in drums rinses the empty drums with water, adds the rinse water to the product stream, then sprays the drums with a sodium hypochlorite bleach solution (converting the 3,3 -dichlorobenzidine to a quinone-type compound), and places them in polyethylene bags for disposal (London and Boiano 1986). 

Other Quinone Types. Although past researchers have examined many coloured quinonoid molecules very few have achieved commercial importance. 

Bacteria have a single reaction center in purple bacteria, it is of the pheophytin-quinone type, and in green sulfur bacteria, the Fe-S type. 

Among the many other substances 1 showing resonance of the semi-quinone type mention may be made of those of the dipyridyl group. 

Among other naturally occurring substances having quinone-type structures, one of the most important is the blood antihemorrhagic factor, vitamin K, which occurs in green plants and is a substituted 1,4-naphthalenedione ... 

Quinone type carriers perform the cotransport of two protons and two electrons (2e, 2H+ symport) [6.48, 6.49] and take part in mitochondrial and photosynthetic electron transport. Cation receptor sites such as crown ethers or cryptands bearing a quinone [6.50a] or a ferrocene [6.50b] group (see also Section 8.3.1), bind and carry cations with redox coupling through switching between a low affinity state (quinone, ferricinium) and a high affinity state (reduced quinone, ferrocene). 

Reduction with zinc powder and sodium hydroxide. Compounds of the anthra-quinone type are reduced to oxanthrols. Treat 0.1 g of the quinone with dilute sodium hydroxide and zinc powder. Upon boiling the mixture a red colour is produced this disappears when the solution is shaken owing to aerial oxidation to the original quinone. 

Aromatic C and quinone C c=o Quinone-type C Protonated and alkylated aromatic C Heteroatom substituted aromatic C Is—Jt 283.0-284.5g,k,q,v... 

Dinuclear complexes of general formula [L(CO)RhQRh(CO)L] [L = PPh3 or CO Q = (34a, b, c) etc.], containing bridging quinone-type ligands, have been synthesized via equation (33).135 I.r. studies support O-co-ordination. Related dimers... 

As shown in Chapter 5, functional groups are always present on the surface of nanoporous carbons. Some of them, as the quinone-type groups, may be involved in reversible redox reactions giving a... 

Achhammer (2) proposed that in addition to above, a second hydroperoxide may form on the benzene nucleus to give a quinone-type compound. 

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