Hydroquinone from benzene

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... 

A Methylamino)phenol. This derivative, also named 4-hydroxy-/V-methy1ani1ine (19), forms needles from benzene which are slightly soluble in ethanol andinsoluble in diethyl ether. Industrial synthesis involves decarboxylation of A/-(4-hydroxyphenyl)glycine [122-87-2] at elevated temperature in such solvents as chlorobenzene—cyclohexanone (184,185). It also can be prepared by the methylation of 4-aminophenol, or from methylamiae [74-89-5] by heating with 4-chlorophenol [106-48-9] and copper sulfate at 135°C in aqueous solution, or with hydroquinone [123-31 -9] 2l. 200—250°C in alcohoHc solution (186). 

Direct production of benzoquinone (BQ) from benzene is one of the targets in industrial chemistry. Considerable efforts have been made to develop the electrochemical oxidation of benzene to p-benzoquinone to the industrial scale thus forming a basis for a new hydroquinone process [40]. Benzene in aqueous emulsions containing sulfuric acid (1 1 mixture of benzene and 10% aqueous H2S04) forms, at the anode, p-benzoquinone which can be reduced cathodically to yield hydroquinone in a paired synthesis. A divided cell with Pb02 anodes is used. 

Hydroprocessing, in petroleum refining, 18 654-657 Hydropulping, 10 535 Hydropyrolysis, coal liquefaction, 6 854 Hydroquinolines, 21 198-199 Hydroquinone (HQ) from benzene, 3 620 as a black-and-white chemical reducing agent, 19 205-206 in bleaching preparations, 7 847 clathrates, 14 160 dye releaser, 19 291-292 inclusion compounds in, 14 172, 174 intermediate used in oxidation hair dyes, 7 858t... 

It has been suggested that phenol exposure results in cardiac effects because it blocks the cardiac sodium channel subtype, with little effect on sodium channels in skeletal muscle (Zamponi et al. 1994). Phenol does not appear to be carcinogenic following oral exposure (NCI 1980), although the chemical combinations that result from benzene and phenol metabolism may contain compounds that do initiate or promote cancer. Metabolites such as hydroquinone and catechol have been demonstrated to be genotoxic and clastogenic. 

To 5.7 g (0.0527 mol) of p-benzoquinone is added 10 g (approximately 0.072 mol) of tin amalgam and 50 ml of glacial acetic acid. The mixture is heated on a steam bath. After 3 minutes green crystals of quinhydrone precipitate but soon dissolve to give a Ught yellow solution. After 0.5 hour the solution is filtered, the solvent is removed in vacuo, and the residue is recrystallized from benzene-acetone to give 5.0g (88%) of hydroquinone, m.p. 169-190°. 

Kennedy and Stock reported the first use of Oxone for many common oxidation reactions such as formation of benzoic acid from toluene and of benzaldehyde, of ben-zophenone from diphenyhnethane, of frawi-cyclohexanediol Ifom cyclohexene, of acetone from 2-propanol, of hydroquinone from phenol, of e-caprolactone from cyclohexanone, of pyrocatechol from salicylaldehyde, of p-dinitrosobenzene from p-phenylenediamine, of phenylacetic acid from 2-phenethylamine, of dodecylsulfonic acid from dodecyl mercaptan, of diphenyl sulfone from diphenyl sulfide, of triphenylphosphine oxide from triphenylphosphine, of iodoxy benzene from iodobenzene, of benzyl chloride from toluene using NaCl and Oxone and bromination of 2-octene using KBr and Oxone . Thus, they... 

Fleszar and Sobkowiak [120] obtained less than 5% of catechol and hydroquinone from the hydroxylation of benzene and phenol on Hg, Pb, Cu, and Ag cathodes, even in the absence of Fe(II). It appears that the generation of H202 occurs even in electrodes where it may undergo catalytic decomposition if there are small quantities of adsorbable substances in solution. 

Diphenyl 5-Hydroxy-l-phen-2-oxide Telluroniuni Zwitterion0.44 g (4 mmol) of hydroquinone are added to a solution of 1.8 g (4 mmol) diphenyl tellurium 4-methylbenzenesulfonimide in 50 m/ anhydrous chloroform. A colorless precipitate separates after 30 min. The mixture is filtered and the filtrate evaporated to dryness under reduced pressure. The solid residue is extracted with 50 ml boiling benzene. The extract is cooled and mixed with 25 ml hexane to precipitate the product, which is recrystallized from benzene/hexane (2 1) yield 60% m.p. HO ... 

Experiments with Benzoquinone,—Benzoquinone was prepared by the oxidation of pure hydroquinone with chromic acid. It was recrystallized twice from benzene and finally sublimed. Only the purest crystals of the sublimed quinone were used for the reactions studied. Since benzoquinone was foimd to sublime very considerably at 110°, it was necessary to dissolve it first in anethol (this was done in a special apparatus filled with pure Ns), then the mixture added to the main apparatus. Benzoquinone was found to react readily with anethol yielding a deep red solution which on heating at 110°, in the absence of oxygen, deposited slowly small quantities of a deep brown amorphous solid, the structure and properties of... 

The catalytic properties of the supported samples were tested in oxidation of cyclohexane and benzene with a mixture of O2/H2 gases at a temperature of 20-40°C. Cyclohexanol and cyclohexanone were obtained from cyclohexane and phenol with admixtures of cyclohexanol and hydroquinone (no more than 2% mol. of each) was obtained from benzene. 

Monomer, flake-like crystals from benzene, d ,1 1-122, mp 84.5 . bp2 87° hps 103° bp2) 125°. Solubilities In g/ (00 ml solvent at 30° water 215.5 methanol 155 ethanol 86.2 acetone 63,1 ethyl acetate 12.6 chloroform 2.66 benzene 0.346 heptane 0.0068. The solid may be stored in a cool, dark place. Readily polymerizes at the mp or under uv light. Commercial sol ns of the monomer may be stabilized with hydroquinone, terr-butylpyrocatechol, N-phenyl-2-naph thylamine or other antioxidants. LD, i.p. in mice 170... 

Analogously, in the presence of silica-supported palladium catalysts, benzene is oxidized under ambient conditions to give phenol, benzoquinone, hydroquinone and catechol [37b]. Palladium chloride, used for the catalyst preparation, is believed to be converted into metallic palladium. The synthesis of phenol from benzene and molecular oxygen via direct activation of a C-H bond by the catalytic system Pd(OAc)2-phenanthroline in the presence of carbon monoxide has been described [38]. The proposed mechanism includes the electrophilic attack of benzene by an active palladium-containing species to to produce a a-phenyl complex of palladium(ll). Subsequent activation of dioxygen by the Pd-phen-CO complex to form a Pd-OPh complex and its reaction with acetic acid yields phenol. The oxidation of propenoidic phenols by molecular oxygen is catalyzed by [A,A"-bis(salicylidene)ethane-l,2-diaminato]cobalt(ll)[Co(salen)] [39]. 

The three isomeric dihydroxybenzenes, C6H4(OH)2, are catechol (pyro-catechin) discovered by H. Reinsch resorcinol by Hlasiwetz and Barth by fusing guaiacum, galbanum, or ammoniacum resins with caustic potash and quinol (hydroquinone) by Pelletier and Caventou (1820) and Wohler (1844 see p. 326). Hydroquinone had been obtained by A. Kawalier, who called it arctuvin , by hydrolysis of the glycoside arbutin (Ci2Hie07) which he discovered in the leaves of the bear-berry. The orientations of the three di-hydroxybenzenes were established by Th. Petersen. Resorcinol was synthesised from benzene by Korner. ... 

Reduction to hydroquinone. Dissolve, or suspend, 0-5 g. of the quinone in 5 ml. of ether or benzene and shake vigorously with a solution of 1 0 g. of sodium hydrosulphite (Na2S204) in 10 ml. of N sodium hydroxide until the colour of the quinone has disappeared. Separate the alkaline solution of the hydroquinone, cool it in ice, and acidify with concentrated hydrochloric acid. Collect the product (extract with ether, if necessary) and recrystalhse it from alcohol or water. 

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). 

Scheme 3b). It is instructive at this point to reiterate that the furan nucleus can be used in synthesis as a progenitor for a 1,4-dicarbonyl. Whereas the action of aqueous acid on a furan is known to provide direct access to a 1,4-dicarbonyl compound, exposure of a furan to an alcohol and an acid catalyst should result in the formation of a 1,4-diketal. Indeed, when a solution of intermediate 15 in benzene is treated with excess ethylene glycol, a catalytic amount of / ara-toluenesulfonic acid, and a trace of hydroquinone at reflux, bisethylene ketal 14 is formed in a yield of 71 %. The azeotropic removal of water provides a driving force for the ketalization reaction, and the presence of a trace of hydroquinone suppresses the formation of polymeric material. Through a Finkelstein reaction,14 the action of sodium iodide on primary bromide 14 results in the formation of primary iodide 23, a substance which is then treated, in crude form, with triphenylphosphine to give crystalline phosphonium iodide 24 in a yield of 93 % from 14.

Validation of the model. Validation of the model was performed using data from rat and mouse liver microsome preparations (Schlosser et al. 1993). The assumption that benzene and its metabolites compete for the same enzyme reaction site was supported in part by the observation of a lag time in the benzene-to-hydroquinone reaction as compared to the phenol-to-hydroquinone reaction. This lag could be explained by the fact that benzene is first hydrolyzed to phenol, which is then hydrolyzed to hydroquinone, and if all compounds are substrates for P-450 2E1, the kinetics of this pathway would be slowed compared to those of the direct phenol-to-hydroquinone pathway. The model also adequately predicted phenol depletion and concomitant hydroquinone formation resulting from phenol incubations. 

Phenol is a tumor promoter in laboratory animals. In mice, dermal exposure to phenol in benzene (Boutwell and Bosch 1959) or in acetone (Salaman and Glendenning 1957 Wynder and Hoffmann 1961) increased the incidence of tumors resulting from dermal exposure to the tumor initiator, DMBA. When injected with mixtures of phenol and hydroquinone, a hydrolyzed metabolite of phenol, mice exhibited significantly depressed bone marrow erythropoiesis compared to injection with phenol alone (Chen and Eastmond 1995a). The involvement of peripheral acetylcholine in phenol-induced tremors was implicated by studies in which mice were injected with phenol and pentobarbital, an inhibitor of acetylcholine release (Itoh 1995). 

There are two dihydroxy benzenes that can result from reaction (3.131)— hydroquinone and pyrocatechol. It has been suggested that they react with oxygen in the following manner [55] ... 

---