Quinol structure

Therapeutic Function Depigmentor Chemical Name 1,4-Benzenedlol Common Name Quinol Structural Formula ... 

The dimer belongs to the rare group of compounds which are piezochromic. Rubbing in a mortar produces a red color due to mechanical bond-breaking and dissociation into the red-colored monomer. The -quinol structure of the 2,4,6-triphenylphenoxyl dimer has been confirmed by infrared studies of i 0-labeled material and by X-ray analysis of 3-bromo derivative. ... 

Quercetin and many 3-hydroxylated flavones, particularly those containing o- or />-quinol structure at ring C, such as (66), are strong antioxidants for unsaturated fatty acids and lipids of vegetable tissues [349-352]. The effect of antioxidant action is decreased when some of the hydroxy groups are methylated [353],... 

This second phase of the inhibition mechanism, which is proved by the isolation of a similar peroxide with quinol structure from monohydric phenols (13,15) is unfavorably affected by steric influence of the present substituent R however, even physical factors will probably influence the activity—e.g., the change in the solubility of the antioxidant in the substrate caused by substitution. The possible resonance of radical VUIb is also illustrated in the scheme. In this case the second radical R OO may be fixed in position 5 (IXb). The reaction may be used to help... 

The projection of the cubic (10, 3) net on a face of the cubic unit cell, the full circles and lines of Fig. 3.28(b), shows that the net is built of 4-fold helices which are all anticlockwise upwards. The figures indicate the heights of the points in terms of c/8, where c is the length of the cell edge. A second net can be accommodated in the same volume, and if the second net is a mirror-image of the first in no case is the distance between points of different nets as short as the distance between (connected) points within a given net. In the second net of Fig. 3.28(b) (dotted circles and lines) the helices are clockwise. This type of structure, which would be a 3D racemate, is not yet known, but in view of its similarity to the /3-quinol structure described later, there is no reason why it should not be adopted by some suitable compound. 

Conversion of Aromatic Rings to Nonaromatic Cyclic Structures. On treatment with oxidants such as chlorine, hypochlorite anion, chlorine dioxide, oxygen, hydrogen peroxide, and peroxy acids, the aromatic nuclei in lignin typically ate converted to o- and -quinoid stmctures and oxinane derivatives of quinols. Because of thein relatively high reactivity, these stmctures often appear as transient intermediates rather than as end products. Further reactions of the intermediates lead to the formation of catechol, hydroquinone, and mono- and dicarboxyhc acids. 

Attempts have been made to deduce the structure of the predominant form of a potentially tautomeric compound from the shifts which occur in the ultraviolet spectrum of the compound in question on passing from neutral to basic or acidic solutions. The fact that no bathochromic shifts were observed for 2- and 4-hydroxy quinoline and 1-hydroxyisoquinoline under these conditions was taken as evidence that they existed in the oxo form [similar work on substituted quinol-4-ones led to no definite conclusions ]. A knowledge of the dissociation constants is essential to studies of this type, and the conclusions can, in any case, be only very tentative. A further dif-... 

A different type of tautomeric relationship exists between compounds of types 323 and 324. Both types of structure can be isolated, pyridones (324, Z = N—Me) and pyrones (324, Z = 0) being formed when 323 (Z = N—Me or 0) is heated with palladium on charcoal in ethylene glycol. Similar isomerizations in the quinol-4-one series have been reported."... 

Ubiquinone or Q (coenjyme Q) (Figure 12-5) finks the flavoproteins to cytochrome h, the member of the cytochrome chain of lowest redox potential. Q exists in the oxidized quinone or reduced quinol form under aerobic or anaerobic conditions, respectively. The structure of Q is very similar to that of vitamin K and vitamin E (Chapter 45) and of plastoquinone, found in chloroplasts. Q acts as a mobile component of the respiratory chain that collects reducing equivalents from the more fixed flavoprotein complexes and passes them on to the cytochromes. 

Figure 18.4 Structures of heme/Cu oxidases at different levels of detail, (a) Position of the redox-active cofactors relative to the membrane of CcO (left, only two obligatory subunits are shown) and quinol oxidase (right), (b) Electron transfer paths in mammalian CcO. Note that the imidazoles that ligate six-coordinate heme a and the five-coordinate heme are linked by a single amino acid, which can serve as a wire for electron transfer from ferroheme a to ferriheme as. (c) The O2 reduction site of mammalian CcO the numbering of the residues corresponds to that in the crystal structure of bovine heart CcO. The subscript 3 in heme as and heme 03 signifies the heme that binds O2. The structures were generated using coordinates deposited in the Protein Data Bank, lari [Ostermeier et al., 1997] Ifft [Abramson et al., 2000] (a) and locc [Tsukihara et al., 1996] (b, c).

Bis(2-methyl-8-quinolinolato)aluminum hydroxide with only two quinolate ligands emits blue color with the maximum peak emission at 485 nm and FWHM of 80 nm [265], Devices fabricated with a structure of ITO/CuPc/NPD/AlMq2OH/LiF/Al give a maximum brightness of 14,000 cd/m2 at 480 mA/cm2. 

From the hind gut of Cetonia aurata an Actinomyces species was isolated which produces the new cytotoxic epoxy quinoles [190] named cetoniacytone A 90 and B 91. In addition, the structurally related aromatic compounds 2,5-di-hydroxy-4-hydroxymethylacetanilide 92 and 2,5-dihydroxy-4-methoxymeth-ylacetanilide 93 were found in minor amounts. 

Ohnishi T, Moser CC, Page CC, et al. 2000. Simple redox-linked proton-transfer design new insights from structures of quinol-fumarate reductase. Structure Folding Design 8 R23-R32. 

In 1988, Nakamura et al. reported the isolation of carbazomycins G (269) and H (270) from the culture broth of Streptoverticillium ehimense. These alkaloids have a structurally unique carbazole-l,4-quinol framework and were obtained from Nature in racemic form. Carbazomycin G showed moderate antifungal activity against... 

Compounds of this sort, in which molecules are entrapped by a lattice formed by other molecules, are called clathrate compounds. Often the lattice is formed by molecules linked to one another by hydrogen bonds. The structures of many of these substances have been determined by Powell and his cowQrkers.6 An especially interesting class is tliat formed by quinol, p-dihydroxybenzene. The hydroxyl groups... 

Similar clathrates occur with many other guests, such as C02, N2O, CH3F and the noble gases. Other hydroxylic compounds besides water can form host structures, benzene-1,4-diol (quinol) being a notable example. 

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