Hydroxyquinones

Note The detection limits for a-hydroxyquinones and 5-hydroxyflavones are 5 pg [1] and for histidine 20 ng substance per chromatogram zone [3]. 

The mechanism of the reaction has not yet been elucidated it is assumed that 1,2-dihydroxybenzene is oxidized to quinone and vicinal trihydroxybenzene derivatives to hydroxyquinones [1]. 

Redox molecules are particularly interesting for an electrochemical approach, because they offer addressable (functional) energy states in an electrochemically accessible potential window, which can be tuned upon polarization between oxidized and reduced states. The difference in the junction conductance of the oxidized and the reduced forms of redox molecules may span several orders of magnitude. Examples of functional molecules used in these studies include porphyrins [31,153], viologens [33, 34,110,114,154,155], aniline and thiophene oligomers [113, 146, 156, 157], metal-organic terpyridine complexes [46, 158-163], carotenes [164], nitro derivatives of OPE (OPV) [165, 166], ferrocene [150, 167, 168], perylene tetracarboxylic bisimide [141, 169, 170], tetrathia-fulvalenes [155], fullerene derivatives [171], redox-active proteins [109, 172-174], and hydroxyquinones [175]. 

Reaction of 1,3-dicarbonyl compounds with vinyl sulfides gives the corresponding medium- and large-sized ring substituted furans 78 in moderate to good yields. In addition to cyclohexane-1,3-diones, 4-hydroxycoumarins and 4-hydroxyquinone can also be used as 1,3-dicarbonyl components . 

This small group of hydroxyquinone (1.16), arylaminoquinone (1.17) and aminophthalimide (1.18) derivatives has contributed a few members of some application ranges, mainly yellow disperse dyes and reddish brown vat dyes, but there are superior alternatives available from the major chemical classes. 

Hydroxypyridine, see Pyridine Hydroxyquinones, see Pentachlorophenol Hydroxysimazine, see Simazine... 

The biological mechanism of action is helieved to involve the production of superoxides near the DNA strand, resulting in DNA backbone cleavage and cell apoptosis. The actual mechanism is not yet known, but is believed to proceed from the reduction of molecular oxygen into superoxide via an unusual auto-redox reaction on a hydroxyquinone moiety of the compound following. There is also some speculation the compound becomes activated into its reactive oxazolidine form. 

The oxygens of methoxynaphthazarin 247 (Scheme 65) (white arrows) can be selectively ortho acetylated/methylated. Starting from the acetates or polyacetates of Scheme 65, it is possible to prepare a variey of polycyclic hydroxyquinone... 

Rueping has further developed this theme by showing that diarylprolinol ether 55 efficiently catalyses the addition of hydroxyquinones to a variety of a,P-unsatu-rated aldehydes as a method for the preparation of both 1,4- and 1,2-naphthoquinones with remarkable levels of enantioselectivity [98],... 

Many quinones derived from aromatic compounds are used as dienophiles in the Diels-Alder reaction, and functionalized hydroxyquinones are extensively used as anti-oxidants in the photo industry and as polymeric materials. 

Percussion caps or detonators are loaded with one or more of the ortho- or para-nitrated quinone diazides of the polymeric phenols or their metallic salts. The K salt of dinitro-m-hydroxyquinone diazide is obtained from nitraminoresorcinol by treatment of the hot... 

The sulfur tetrafluoride fluorination of most nonhalogenated quinones and hydroxyquinones is erratic in behavior and generally occurs with isomerization, substitution of a hydrogen atom by fluorine, and addition of fluorine to the carbon atom / to the carbonyl group. Thus, the fluorination of benzo-l,4-quinone results in aromatization to give 1,2,4-trifluorobenzene (8) as the sole product.41... 

Humic acido from ooilo and ligniteo have been examined by ERR spectrometry. All samples showed a stable free organic radical content of about 1018 spins per gram. When these samples were converted to their sodium salts, a marked increase in radical content occurred. This was interpreted to indicate that a quinhydrone moiety exists in the humic acid macromolecule. Synthetic humic acid, prepared by oxidizing catechol in the presence of amino acids, also showed similar ERR spectra, as did selected quinhydrone model compounds. The radical moiety appeared to be stable to severe oxidation and hydrolytic conditions. Reduction in basic media caused an initial decrease in radical species continued reduction generated new radical species. A proposed model for humic acid based on a hydroxyquinone structure is proposed. 

Controlled electrolytic reduction of humic acid and hydroxyquinones in dimethylformamide in our laboratory (27) have shown small initial decreases in spin content followed by an increase up to the first half-wave potential. Since this was carried out in the absence of base, it would correspond to the portion of the curve in Figure 7 after the first maximum. The probable series of competing reactions is illustrated in Figure 8. Austen and co-workers (1) have observed similar behavior in coal extracts that were electrolytically reduced. 

An EPR spectral survey of a selected number of hydroxyquinones showed that they all formed stable radical salts which could be reversibly converted to the acid form of low or negligible spin content. Significantly, many of these hydroxyquinones were stable free radicals in the acid form although the radical content was quite low (Table IV). 

Wolfgang Flaig. You formulated the hydroxyquinone radical as an oxygen radical. Do you observe ether linkages after polymerization ... 

In a recent study S. E. Moschopedis (II) produced some direct evidence for the presence of quinones and hydroxyquinones in coal and humic acid, and infrared examination of products obtained in the course of the present investigation clearly indicated the existence of five-membered cyclic anhydrides in the reactant mixtures. 

Quinone Diazides. E. von Herz (Ref 1) proposed the use of nitrated quinone diazides and tetra-zides of polyhydric phenols or their metallic salts in percussion caps and primers, either as a top charge over a main charge (Tetryl, PETN or TNT), or in mixts with usual primary expls such as LA, MF, etc. Typical compds were 4,6-dinitro-2-quinone diazide, the K salt of dinitro-3-hydroxy quin one diazide, metallic salts of dinitro-4-hydroxyquinone diazide, the Pb salt of dinitro-3,5-dihydroxyquinone diazide, and sym-tetra-nitrodihydroxydiphenylolquinone tetrazide J.E. Burns (Ref 2) proposed the use of nitrated quinone diazides, such as the 2,6-dinitro-2-diazide, with Pb pic rate, Na nitrate, Pb thio-... 

Conjugate addition of acyl groups to naphthoquinones (3, 211).2 The acyl nickel carbonylate anion (1) undergoes conjugate addition to the ethylene ketal 2 to form a lithium adduct that can be trapped by allyl iodide to give 3 in 81% yield. This product can be converted in a few steps to the hydroxyquinone 4, a precursor of the naphthoquinone antibiotic deoxyfrenolicin (5). 

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