P-Dihydroxybenzene

Chemical Designations - Synonyms 1,4-Benzenediol p-Dihydroxybenzene Hydroquinol Pyrogentisic acid Quinol Chemical Formula 1,4-CjH4(OH)2. 

Dihydroxybenzene, see Elydroquinone p-Dihydroxybenzene, see Elydroquinone Diisocyanatoiuene, see 2,4-Toiuene diisocyanate... 

Hydroquinone, Hydroquinol, 1,4-Benzenediol or p-Dihydroxybenzene (Hydrochinon in Ger). See 1,4-Dihydroxybenzene in Vol 5 of Encycl, p D1270-R... 

Compounds of this sort, in which molecules are entrapped by a lattice formed by other molecules, are called clathrate compounds. Often the lattice is formed by molecules linked to one another by hydrogen bonds. The structures of many of these substances have been determined by Powell and his cowQrkers.6 An especially interesting class is tliat formed by quinol, p-dihydroxybenzene. The hydroxyl groups... 

Oxidation of hydroquinone derivatives (p-dihydroxybenzenes) with Cr(VI) reagents is a method for preparing quinones. 

DIHYDROXYBENZEN (CZFXH) see HIHOOO DIHYDROXYBENZENE see HIHOOO m-DIHYDROXYBENZENE see REAOOO o-DIHYDROXYBENZENE see CCP850 p-DIHYDROXYBENZENE see HIHOOO... 

Synonym 1,4-benzenediol, p-dihydroxybenzene, p-hydroxyphenol, quinol, hydroquinol... 

Quinones are an interesting and valuable class of compounds because of their oxidation-reduction (redox) properties. They can be easily reduced to hydLroquinones (p-dihydroxybenzenes) by reagents such as NaBH4 and SnCl2, and hydroquinones can be easily reoxidized back to quinones by Fremy s salt. 

Dexamethasone and betamethasone are isomeric fluorinated derivatives of methyl-prednisolone, but their solubilities are not identical, which might be a crystal property or a solution property. A simpler example of differences in isomeric solubility is that of the 0-, m-, and p-dihydroxybenzenes referred to above. A steric argument may be applied to the case of dexamethasone, water molecules being less able to move close to the 17-OH group than in the case of betamethasone. 

As an example of a unit of type (e) of Fig. 3.20 we illustrate diagrammatically the structure of one of the polymorphs of quinol, p-dihydroxybenzene. Each OH group can act as the donor and acceptor end of an 0-H--0 bond, and the simplest arrangement of molecules of this kind is the plane layer illustrated in Fig. 3.26. The structures we have described are summarized in Table 3.11. 

Water can be used as the hydrogen source in reduction of p-benzoqui-none to p-dihydroxybenzene in the presence of the anionic platinum cluster [Pt12(CO)24]2... 

Ethyl-1,3-hexanediol Thiodiglycol Butoxytriglycol p-Dihydroxybenzene (hydroquinone)... 

Hydroquinone is 1,4-benzenediol. Hydroquinone is structurally related to monobenzone. Hydroquinone occurs as fine, white needles. The drug is freely soluble in water and in alcohol and has a pKa of 9.96. Chemically, hydroquinone is designated as p-dihydroxybenzene the empirical formula is C6H602. 

Crystallization of solutions of quinol [p-dihydroxybenzene, p-C6H4(OH)2] in water or alcohol under pressure of 10-40 atm of, say, krypton, produces crystals, often up to 1 cm in length, which are readily distinguishable from the crystals of ordinary quinol (a-quinol), even visually. These crystals contain the noble gas trapped in the lattice of -quinol. When the crystals are dissolved in water, or heated, the gas is released. The crystals are stable at room temperature and can be kept for years. 

The original commercial application of TS-1 was the oxidation of phenol in the presence of TS-1 using hydrogen peroxide as the oxidant (45). The main products are a mixture of hydroquinone (p-dihydroxybenzene) and catechol (o-dihydroxyben-zene) (Fig. 10.12). It has been observed that the selectivity and activity of the TS-1 catalyst is tied to the points above. Further, although other titanium-containing zeolites have been investigated [e.g. Ti-Beta (BEA), Ti-ZSM-12 (MTW) Reference 46] none display the activity and selectivity of TS-1. One possible explanation for this is pore size effects another possibility is that the TS-1 samples, which are quite hydrophobic. 

The hydroxylation of phenol to hydroquinone and catechol was the first commercial application of TS-1 by ENI (218,219b). The reaction, which occurs in aqueous or aqueous-organic solutions, produces a mixture of hydroquinone (p-dihydroxybenzene) and catechol (o-dihydroxybenzene). Water and tarry compounds are the major by-products. 

Synonyms 1,4-Benzenediol p-Benzenediol Benzohydroquinone Ben-zoquinone p-Benzoquinone Dihydroxybenzene 1,4-Dihydro) n-zene p-Dihydroxybenzene HQ Hydr uinol p-Hydroquinone 1,4-Hydroxybenzene p-Hydrorq phenol Hydroxyquinone Paradior n-zene Pyrogentistic acid Quinol Classification Aromatic organic compd. aromatic alcohol Enpirical CeHsOj Fwrmda C6H4(OH)2... 

Dihydroxybenzene. See Hydroquinone m-Dihydroxybenzene. See. Resorcinol o-Dihydroxybenzene. See Pyrocatechol p-Dihydroxybenzene. See Hydroquinone... 

Dihydroxybenzene 1,4-Dihydroxybenzene p-Dihydroxybenzene HQ Hydroquinol p-Hydroquinone 1,4-Hydroxybenzene p-Hydroxyphenol Hydroxyquinone Paradioxybenzene Pyrogentistic acid Quinol... 

Hydroquinone (p-dihydroxybenzene) was first produced by Pierre Joseph Pelletier and Jean Caventou in 1820, by dry distillation of quinic add. The structure was elucidated by Friedrich Wohler in 1844. 

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