1.4- Dihydroxybenzene, from

Polystyrenes cross-linked with divinylbenzene commercial resins, such as Lewatit VP-OC 1163 (Bayer AG, Leverkusen, Germany), Amberlite XAD-4 (Rohm Haas, Frankfurt, Germany), and Serdolite PAD I, PAD II, and PAD III (Serva AG, Heidelberg, Germany), have been applied in the adsorption of phenol, chlorophenols, and dihydroxybenzenes from water solutions [90]. Besides, commercial polymethacrylate/divinylbenzene resins, for example, Supelcogel TPR-100... 

Supelco, Deisenhofen, Germany) have been investigated in the adsorption of phenol, chlorophe-nols, and dihydroxybenzenes from water solutions [90],... 

This process has been widely studied and led to the constmction of new and original industrial units. Interest in the reaction stems from the simplicity of the process as well as the absence of undesirable by-products. However, in order to be economically rehable, such a process has to give high yield of dihydroxybenzenes (based on hydrogen peroxide as well as phenol) and a great flexibiUty for the isomeric ratio of hydroquinone to catechol. This last point generated more research and led to original and commercial processes. 

Pyrolysis ofVegetals. Many pubhcations concern the synthesis of dihydroxybenzenes by wood, lignites, and tree bark pyrolysis (61). The selective extraction of these compounds in low concentration from the cmde mixture remains a significant problem. So far, the price of the extraction overcomes the advantage of starting from a cheap starting material. 

Starting from Benzene. In the direct oxidation of benzene [71-43-2] to phenol, formation of hydroquinone and catechol is observed (64). Ways to favor the formation of dihydroxybenzenes have been explored, hence CuCl in aqueous sulfuric acid medium catalyzes the hydroxylation of benzene to phenol (24%) and hydroquinone (8%) (65). The same effect can also be observed with Cu(II)—Cu(0) as a catalytic system (66). Efforts are now directed toward the use of Pd° on a support and Cu in aqueous acid and in the presence of a reducing agent such as CO, H2, or ethylene (67). Aromatic... 

Other Methods. A variety of other methods have been studied, including phenol hydroxylation by N2O with HZSM-5 as catalyst (69), selective access to resorcinol from 5-methyloxohexanoate in the presence of Pd/C (70), cyclotrimerization of carbon monoxide and ethylene to form hydroquinone in the presence of rhodium catalysts (71), the electrochemical oxidation of benzene to hydroquinone and -benzoquinone (72), the air oxidation of phenol to catechol in the presence of a stoichiometric CuCl and Cu(0) catalyst (73), and the isomerization of dihydroxybenzenes on HZSM-5 catalysts (74). 

In the case of low temperature tar, the aqueous Hquor that accompanies the cmde tar contains between 1 and 1.5% by weight of soluble tar acids, eg, phenol, cresols, and dihydroxybenzenes. Both for the sake of economics and effluent purification, it is necessary to recover these, usually by the Lurgi Phenosolvan process based on the selective extraction of the tar acids with butyl or isobutyl acetate. The recovered phenols are separated by fractional distillation into monohydroxybenzenes, mainly phenol and cresols, and dihydroxybenzenes, mainly (9-dihydroxybenzene (catechol), methyl (9-dihydtoxybenzene, (methyl catechol), and y -dihydroxybenzene (resorcinol). The monohydric phenol fraction is added to the cmde tar acids extracted from the tar for further refining, whereas the dihydric phenol fraction is incorporated in wood-preservation creosote or sold to adhesive manufacturers. Naphthalene Oils. Naphthalene is the principal component of coke-oven tats and the only component that can be concentrated to a reasonably high content on primary distillation. Naphthalene oils from coke-oven tars distilled in a modem pipe stiU generally contain 60—65% of naphthalene. They are further upgraded by a number of methods. 

In this paper we present the relative energies of the isomers of the phenylenediamines, dihydroxybenzenes and difluorobenzenes from ab initio calculations using large basis sets and including correlation corrections at the MP-2 level. These calculations were done at the geometry optimized structures. We also include zero-point energy corrections based on our calculated force fields. 

The enzymes catalyzing the Kolbe-Schmitt carboxylation seem to occur ubiquitously. Some of them, such as 2,6-dihydroxybenzoate decarboxylase and pyrrole-2-carboxylate decarboxylase, catalyze efficiently the reverse carboxylation reaction and accumulate high concentration of 2,6-dihydroxybenzoate from 1,3-dihydroxybenzene and pyrrole-2-carboxylate from pyrrole, respectively, in the... 

Mercapto-l,2,4-triazole 67 reacted in a standard coulometric cell with the ortho-quinone generated electroche-mically from 1,2-dihydroxybenzene to give 4-(l//-l,2,4-triazole-3-ylsulfanyl)-l,2-benzenediol 68 via a Michael addition (Equation 23) <2005MI68>. 

This conclusion is supported by results of detailed study on the decay of hydroxyhexa-dienylperoxyl radicals, formed by addition of OH to benzene, followed by addition of dioxygen molecule. It was found that in the high dose rate of pulse radiolysis, hydro-quinone is the major product whereas catechol was not observed, indicating that only the 1,3-isomer loses HO2" and hence does not lead to dihydroxybenzene. The observation that the yield of 02 is 60% of the yield of the cyclohexadienyl radicals indicates that when dioxygen molecules react with the cyclohexadienyl radical, the radical is 60% trapped in the mesomeric form of 5b, whereas the results from the final products of dimerization in /-radiolysis show that 60% react in the form 5a. 

As we presented above, the presence of quartz in the temperature range studied had no effects on the decomposition of dihyroxybenzenes. To further investigate this point and show the different effects of iron oxide and quartz on the product distribution, we present the product distribution for two cases of nanoparticle iron-oxide mixed with quartz chips and only quartz chips. Comparison in product distribution over nanoparticle iron oxide/quartz mixture and quartz was carried out with 3% of oxygen andl8 x 10 mmol/min of feedrate for starting materials, and at reaction temperatures that resulted in a comparable conversion of dihydroxybenzenes (e.g., 80%). Figure 12.6 shows the average spectra of the products obtained from MBMS for two cases with about 80% catechol conversion that was achieved at 300°C in the presence of iron oxide... 

M. J. Wornat, E. B. Ledesma, and N. D. Marsh, PolycycUc aromatic hydrocarbons from the pyrolysis of catechol (ordio-dihydroxybenzene), a model fuel representative of entities in tobacco, coal, and lignin, Fuel 80,1711-1726 (2001). 

One of the earliest reports of LO inhibition concerned the effects of ortho-dihydroxybenzene (catechol) derivatives on soybean 15-LO [58]. Lipophilic catechols, notably nordihydroguaiaretic acid (NDGA) (19), were more potent (10 /zM) than pyrocatechol itself. The inactivation was, under some conditions, irreversible, and was accompanied by oxidation of the phenolic compound. The orfAo-dihydroxyphenyl moiety was required for the best potency, and potency also correlated with overall lipophilicity of the inhibitor [61]. NDGA and other phenolic compounds have been shown by electron paramagnetic resonance spectroscopy to reduce the active-site iron from Fe(III) to Fe(II) [62] one-electron oxidation of the phenols occurs to yield detectable free radicals [63]. Electron-poor, less easily oxidized catechols form stable complexes with the active-site iron atom [64]. 

Anticipated products from the reaction of phenol with ozone or OH radicals in the atmosphere are dihydroxybenzenes, nitrophenols, and ring cleavage products (Cupitt, 1980). Reported rate constants for the reaction of phenol and OH radicals in the atmosphere 2.8 x 10 " cmVmolecule-sec at room temperature (Atkinson, 1985) and with NO3 in the atmosphere 2.1 x lO" cmVmolecule-sec at 296 K (Atkinson et al., 1984). 

PVC, polyamides, unsaturated crosslinked polyesters, ABS, and wood . Di- and tri-benzotriazole photostabilizers, such as (874) and (875) are synthesized from 2-nitro-benzenediazonium salts and an excess of 1,3-dihydroxybenzene or 1,3,5-trihydroxybenzene <85Mi 40i-0l>. The dibenzotriazole derivatives (874b and 875b) can be used as polymerizable acrylic UV absorbers <84PB237>. A few or/Ao-urethane and -trimethylsilane substituted 2-phenylbenzotriazoles (876 and 877) show similar photostabilization activity . Weather resistance of low-density polyethylene is improved by the addition of a benzotriazole-type photostabilizer <90M140i-04>. 

Benzotrithiole 2-oxide (41) was obtained in 76% yield from the reaction of benzene-1,2-dithiol with thionyl chloride <93TL673>. Similarly, 1,3,2-benzodioxathiole 2-oxide was prepared from 1,2-dihydroxybenzene and thionyl chloride <66HC(2i-i)i>, and 1,2,3-benzoxadithiole 2-oxide was obtained from 2-mercaptophenol and thionyl chloride <81AG(E)570>. Reaction of the monosodium salt of 1,2-dihydroxybenzene with sulfuryl chloride afforded an intermediate chlorosulfate ester, which was dehydrochlorinated to 1,3,2-benzodioxathiole 2,2-dioxide by the action of pyridine <66HC(21-l)l>. The substituted 1,3,2-benzodioxathiole 2,2-dioxide (121) was isolated from the photolysis of pyrenedione in the presence of sulfur dioxide <87TL2057>. 

METHYL-l-METHYLENE-2-(r-METHYLETHYL)-, R,R-), 65, 81 MICHAEL ADDITION, APROTIC, 66, 37, 41 cis.cis-Monornethyl muconate (61186-96-7), 66, 180, 184 cis.cis-MONOMETHYL MUCONATE FROM 1,2-DIHYDROXYBENZENE, 66. 180... 

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