Quinones quinols

Synonyms AI3-00072 Arctuvin p-Benzenediol 1,4-Benzenediol Benzohydroquinone Benzoquinol Black and white bleaching cream BRN 0605970 CCRIS 714 Dihydroxybenzene jO-Dlhydroxybenzene 1,4-Dihydroxybenzene p-Dioxobenzene EINECS 204-617-8 Eldopaque Eldoquin HQ Hydroquinol Hydroquinole a-Hydroquinone p-Hydroquinone 4-Hydroxy-phenol p-Hydroxyphenol NC1-C55834 NSC 9247 Quinol p-Quinol Quinone Tecquinol Tenox HQ Tequinol UN 2662 USAF EK-356. 

Puupehenone (63) is a member of a distinctive family of sponge metabolites — a sesquiterpene joined to a C6-shikimate moiety — first exemplified by the quinol-quinone pair of avarol and avarone. Among the varied activities that have been reported for this diverse class of compounds is the property of ilimaquinone to inhibit replication of the HIV virus.78 Preliminary screening of puupehenone against Mycobacterium tuberculosis showed 99% inhibition of the organism. A series of chemical modifications have been conducted on puupehenone to study the effect on its biological activity. 

Fig. 13. Relationships between lipophilic antioxidants and lipid hydroperoxides in irradiated skin. (A) There was no relationship between decrease in a-tocopherol and appearance of lipid hydroperoxides. (B) There was a significant (p < 0.05) relationship between decrease in total Q (quinols + quinones) and appearance of lipid hydroperoxides.

Q-pool outside. The minimum distance between myxothiazol and an-timycin A molecules is only 18 A this indicates that the two sites can exchange a quinol/quinone molecule very quickly by simply flipping the head group. 

Phenolic oxidation is known to be effected with sodium periodate or periodic acid to yield o- and p-quinols, quinones and other products, depending on substituents attached to the aromatic ring. 2,4,6-Trimethylphenol (221) was subjected to NaI04 oxidation in 80% aq. AcOH to afford the four products 383, 599, 600 and 601 (10, 17, 28 and 31%, respectively). Of these products, the dimer 601 must be formed from the corresponding cyclohexadienone 602 (Scheme 115) °. ... 

It is well known that HQNO raises the midpoint potential(s) of haem(s) b of the mitochondrial bc complex [12]. It was therefore necessary to determine whether HQNO sterically inhibited the mitochondrial quinone reduction site directly or simply prevented the forward reaction because of the raised values. This was tested by its effect on (a) duroquinol or ubiquinol reduction of haem b in the presence of the Q -site inhibitor, myxothiazol (b) the quinol-quinone transhydrogenase activity of the quinone reduction site. In both of these cases, raising of the midpoint potentials of the haems b might have been expected to stimulate activity. However, HQNO was found to potently inhibit both of these reactions, demonstrating that it did indeed directly inhibit the quinone reduction site, a result commensurate with its inhibitory effect on steady state flux through the enzyme. 

The intravenous anaesthetic propofol (2,6-diisopiopylphenol) and five metabolites (2,6,-diisopryopyl-l,4-quinol and 1,4-quinone, the quinol sulfate and glucur-onide, and propofol glucuronide) were recovered from urine and separated on a 25°C Cig column (A = 270 nm or 230 nm) using a 35-min 87/13 - 11/89 water (acetic acid to pH 3.8)/acetonitrile gradient [1469]. Similarly, propofol (2,6-diisopropyl-phenol) and six metabolites (quinol, quinone, quinol-4-sulfate, and propofol-1-. 

Pt Calomel FeCl2 Quinol Cb quinol Quinone P-NH20OH 02NH ... 

Kwak, (.H Schmitz, F.( and Kelly, M. (2000) Sesquiterpene quinols/ quinones from the Micronesian sponge Smenospongia metachromia. J. Nat Prod, 63,1153-1156. 

Reduction, (a) By sulphurous acid. Benzoquinone, /> toluquinone, 1,2-naphthoquinone are readily reduced by SOj ultimately to the dihydroxy-compound. Thus benzoquinone gives colourless hydro-quinone or quinol, />-C2H4fOH)2. 

Electron Transport Between Photosystem I and Photosystem II Inhibitors. The interaction between PSI and PSII reaction centers (Fig. 1) depends on the thermodynamically favored transfer of electrons from low redox potential carriers to carriers of higher redox potential. This process serves to communicate reducing equivalents between the two photosystem complexes. Photosynthetic and respiratory membranes of both eukaryotes and prokaryotes contain stmctures that serve to oxidize low potential quinols while reducing high potential metaHoproteins (40). In plant thylakoid membranes, this complex is usually referred to as the cytochrome b /f complex, or plastoquinolplastocyanin oxidoreductase, which oxidizes plastoquinol reduced in PSII and reduces plastocyanin oxidized in PSI (25,41). Some diphenyl ethers, eg, 2,4-dinitrophenyl 2 -iodo-3 -methyl-4 -nitro-6 -isopropylphenyl ether [69311-70-2] (DNP-INT), and the quinone analogues,... 

Quinone and Quinol. (ininonc, which weis oiiginally obtai ied h the oxiilation of quinlt acid (the add associated... 

Fe7-ric chloride reaclion.—Dissolve a drop of the free phenol in water and add a drop of ueutral ferric chloride. A green (catechol), blue (orcinol, pyiogallol) or purple (phenol, resorcinol) colouration is produced, which is often destroyed by acid or alkali. Quinol is o.xidised to quinone, and turns biown (p. 193). The naphthols give precipitates of dinaphthol (p. 220). 

Benzenediol, quinol, or p-dihydroxy benzene [CgH4-l,4-(OH)2] has a MW of 110.1. It is a white crystalline powder formed by the reduction of p-benzoquinone [quinone, CgH4 ( 0)2],... 

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 18.2 Summary of respiratory energy flows. Foods ate converted into the reduced form of nicotinamide adenine dinucleotide (NADH), a strong reductant, which is the most reducing of the respiratory electron carriers (donors). Respiration can he based on a variety of terminal oxidants, such as O2, nitrate, or fumarate. Of those, O2 is the strongest, so that aerobic respiration extracts the largest amount of free energy from a given amount of food. In aerobic respiration, NADH is not oxidized directly by O2 rather, the reaction proceeds through intermediate electron carriers, such as the quinone/quinol couple and cytochrome c. The most efficient respiratory pathway is based on oxidation of ferrocytochrome c (Fe ) with O2 catalyzed by cytochrome c oxidase (CcO). Of the 550 mV difference between the standard potentials of c)Tochrome c and O2, CcO converts 450 mV into proton-motive force (see the text for further details).

Wang, J. Pettus, L. H. Pettus, T. R. R. Cycloadditions of o-quinone dimethides with p-quinol derivatives regiocontrolled formation of anthracyclic ring systems. Tetrahedron Lett. 2004, 45, 1793-1796. 

Anthraquinol + 02 —i> Anthraquinone + H202 The anthraquinone derivative is usually 2-ethyl- or 2-pentyl-anthraquinone. The solvent is usually a mixture of two solvents, one for the quinone and one for the quinol. The... 

Me3SiCN reacts with both saturated and unsaturated aldehydes and ketones to given silylated cyanohydrines. This reaction has been particularly useful for the regioselective protection of a carbonyl in p. quinones and p. quinol antibiotic metabolite has been prepared. 

Quinone is produced in small yield by direct oxidation of benzene itself with silver peroxide, but better by the action of oxidising agents on a large number of its p-disubstitution products. Thus, in addition to quinol, p-aminophenol (experiment, p. 176), p-anisidine, p-toluidine, and sulphanilic acid as well as p-phenylenediamine and many of its derivatives yield quinone in this way. 

The great affinity of quinone for hydrogen leads to the formation of anilinoquinone which can now, in the same way, add a further equivalent of aniline to the half of the molecule not yet involved. The dianilino-quinol is converted into dianilinoquinone in the same way as the first reaction product was changed. (Write the equation.)... 

Experiment.—Qninol from Quinone. Suspend about 2 g. of quinone in 50 c.c. of water and while shaking frequently saturate the suspension with sulphur dioxide. Keep for some time and then extract the now colourless liquid twice with ether, dry the ethereal extract with calcium chloride, and evaporate the ether. The residue of quinol crystallises. Recrystallise it from a little water. Melting point 169°. Warm a sample with dilute sulphuric acid and a few drops of dichromate solution the odour of quinone is emitted. 

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