P-Dihydroxy benzene

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],... 

Figure 8.1 The old and the new manufacturing processes for p-dihydroxy benzene. Route (a) is the old process, which involves stoichiometric oxidation, while route (b) involves catalytic oxidation. The amount of solid waste generated in (a) is an environmental hazard.

The influence of substituents on the solubility of molecules in water can be due to their effect on the properties of the solid or liquid (for example, on its molecular cohesion) or to the effect of the substituent on its interaction with water molecules. It is not easy to predict what effect a particular substituent will have on crystal properties, but as a guide to the solvent interactions, substituents can be classified as either hydrophobic or hydrophilic, depending on their polarity (see Table 5.4). The position of the substituent on the molecule can influence its effect, however. This can be seen in the aqueous solubilities of o-, m- and p-dihydroxy-benzenes as expected, all are much greater than that of benzene, but they are not the same, being 4, 9 and 0.6 mol dm, respectively. The relatively low solubility of the para compound is due to the greater stability of its crystalline state. The melting points of the derivatives indicate that is so, as they are 105°C, 111°C, and IZO C, respectively. In the case of the ortho... 

In the quinol clathrates the molecules of quinol (p-dihydroxy-benzene) are again linked by hydrogen bonds between rings of six hydroxyl groups, but now such linkages take place at both ends of the molecule and bind the molecules into infinite three-dimensional frameworks of the form shown in fig. 14.33. This framework is very open, and in the crystal two such frameworks exist, completely interpenetrating... 

Dihydroxybenzenes and trihydroxybenzenes such as l,2-dihydroxy-4-t-butylbenzene, 1,2,3-trihydroxybenzene, and hydroquinone (p-dihydroxy-benzene) act as inhibitors in the presence of oxygen [7,8] The inhibiting effect of these compounds is produced by their oxidation to quinones [9]. 

A solution of 30 parts by weight of pinacolin alcohol in ether is saturated with hydrogen chloride at room temperature and the ether solution then agitated with bicarbonate. After concentration by evaporation it leaves behind the crude diethylstilbestrol [a,j3-(p,p -dihydroxy-diphenyl)-Oi, 3from benzene, melts at 170°C to 171 °C. The yield amounts to 75% of the calculated. The total y eld of diethylstilbestrol, calculated on p-hydroxypropiophenone, is 68% of the theoretical. 

Synonyms 1,4-Benzenediol 1,4-dihydroxy-benzene p-hydroxybenzene hydroquinol quinol Tecquinol... 

Diplumbic Dinitroresorcinol. See Basic Lead Salt of 4,6-Dinitro-l, 3-dihydroxy benzene or Lead 4,61 Din itro resorcin ate, p D1275-.R... 

BENZENE, 1,2-DICHLORO- see DEP600 BENZENE, o-DIETHOXY- see CCP900 BENZENE, l,2-DIETHOXY-(9CI) see CCP900 BENZENE, p-DIHYDROXY- see HIHOOO BENZENE-l,3-DIISOCYANATE see BBPOOO BENZENE-1,3-DIISOCYANATE see BBPOOO BENZENE, 1,3-DIISOCYANATO- see BBPOOO BENZENE-, 1,3-DIISOCYANATOMETHYL- see TGM740... 

Hydro-quinol, 1-4-Di-hydroxy Benzene.—The third isomeric dihydroxy benzene, viz., the para compound, i-4-di-hydroxy benzene, is known as hydro-quino or hydro-quinone. The latter name is derived from its relation to quinone (p. 636) from which it is obtained on reduction and which it yields on oxidation. Both hydro-quinol and quinone derive their names from the fact that they are obtained by the oxidation of quinic acid, an acid derived from the alkaloid quinine. The phenol is found in various plants or may be obtained from them by the hydrolysis of glucosides present, e.g., arbutin, which is a glucoside hydrolyzing into glucose and hydro-quinol. 

Resorcinol, dihydroxy benzene, and naphthols both a and P, are the most important hydroxy-aromatics having wide applications and are produced from benzene and naphthalene, respectively, using similar technologies as in production of synthetic phenol from benzene or cresols from toluene. It may be relevant to discuss briefly about these products. 

The monocation dimer of coronene (Willigen et al., 1968) and pyrene (Cooper and Forbes, 1968) have been detected by esr spectroscopy in S03-BF3 solution at low temperatures. Broad bands in the region of 500- 600 nm in spectra of p-dihydroxy- and p-dialkoxybenzenes (e.g. hydroquinone, 1,4-dimethoxybenzene) in sulfuric acid at 77°K have been attributed to the presence of Mj4" by Yamada and Kimura (1969), while Carter and Vincow (1967a) observed by esr (benzene)i+ in irradiated solutions of benzene in sulfuric acid at —103°. Using a flow-system, it was found by esr spectroscopy that the oxidation of mcsitylene by cobalt(III) tri-fluoroacetate in TFA solution led to Mj+ rather than M + signals (Shih and Dessau, 1971). 

PET is the key feature of many other photo-oxidations involving aromatic substrates. It has been shown, for example, that pyrene and anthracene which are covalently attached to silica, gold or indium-doped tin oxide (ITO), undergo a photo-oxidation forming dihydroxy/dione derivatives. The reaction involves 02, formed by ET between excited pyrene, or anthracene, and O2, and it is suggested that the implications of such a photodegradation need to be considered when polycyclic aromatic hydrocarbons (PAHs) are used as spectroscopic probes in surface adlayers. The redox photosensitized amination of 1,2-benzo-1,3-cycloalkadienes, arylcyclopropanes, and quadricyclane with ammonia and primary amines, using 1,2,4-triphenylbenzene (1,2,4-TPB) or 2,2 -methylenedioxy-1,1 -binaphthalene in the presence of m- or p-dicyano-benzene (DCB), has been described (Scheme 51). The process involves the formation of the radical cation of 1,2,4-TPB, for example, by PET to the DCB, followed by hole transfer from the radical cation to the substrate, the latter... 

Additives to effect curing can be used. These include o-dihydroxy-benzene, p-quinone and quinhydrone. ... 

Addition. Arbutin. 4-0-P-D-Glucopyranosylhydroquinone (arbutin), discovered as a major metabohte of the leaves of Arctostaphylos uva-ursi (L.) Spreng., bear-berry (Ericaceae), was detected as one of the soluble phenoUcs in fungus-infected leaves of S. tuberosum (BfeUo- et al. 1996). Its aglycone hydioquinone (1,4-dihydroxy-benzene) represents a CgC derivative of the benzenoid metabohsm (oxidative decarboxylation of p-hydroxybenzoic acid). 

Strictly speaking, it should be named as a,a-dihydroxy-p-diisopropyl-benzene, a tertiary aromatic dialcohol. The name dicumyl alcohol is used for convenience. 

A new approach to the resolution of sulphoxides 242 was recently reported by T oda and coworkers282. It takes advantage of the fact that some sulphoxides form crystalline complexes with optically active 2,2 -dihydroxy-l, 1-binaphthyl 243. When a two-molar excess of racemic sulphoxide 242 was mixed with one enantiomeric form of binaphthyl 243 in benzene-hexane and kept at room temperature for 12 h, a 1 1 complex enriched strongly in one sulphoxide enantiomer was obtained. Its recrystallization from benzene followed by chromatography on silica gel using benzene-ethyl acetate as eluent gave optically pure sulphoxide. However, methyl phenyl sulphoxide was poorly resolved by this procedure and methyl o-tolyl, methyl p-tolyl, s-butyl methyl and i-propyl methyl sulphoxides did not form complexes with 243. 

The reaction mixture from acidified dihydroxyacetone also included a series of seven di- and tri-hydroxybenzenes (see Scheme 4), namely, 2,3-dihydroxytoluene (16), pyrocatechol (17), 3,4-dihydroxy toluene (19), 3,5-dimethyl-l,2-benzenediol (20), 1,2,3-trihydroxybenzene (pyrogallol) (21), 1,2,4-trihydroxy benzene (22), 3,4,5,6-tetrahydroxy-2-methy 1-acetophe-none, and 2,3-dihydroxy-5,6-dimethyl-p-benzoquinone. Many of these same phenolic compounds are present after hexoses are similarly treated... 

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