1,3-Dihydroxybenzene. See

Resorcinol (1,3-Dihydroxybenzene). See under Dihydroxylbenzene and Derivatives in Vol 5, D1270-R... 

The benzenedisulfonic acids are of little interest, except that benzene-1,3-disulfonic acid is a source of 1,3-dihydroxybenzene (see Chapter 4). The benzene dicarboxylic acids are more important. Benzene-1,2-dicarboxylic acid (phthalic acid, 8) can be converted into phthalic anhydride (9), which is a typical acid anhydride, reacting with amines and alcohols and also taking part in Friedel-Crafts reactions. Phthalimide (10), produced by reaction of the anhydride with ammonia, is weakly acidic and forms a potassium salt with ethanolic potassium hydroxide. 

Resorcinol see 1,3-Dihydroxybenzene Resorcinol homologues 290 Resorufin, pH-dependent change of fluorescence color 91... 

The complex l,l -bis(ethenyl -pyridyl)ferrocene was also co-crystallized with 1,3-dihydroxybenzene (resorcinol) and 1,3,5-trihydroxybenzene (phloroglucinol)" to form hydrogen-bonded molecular clips (see Figure 12), which lock the conformation of the organometallic fragment in a dipolar arrangement, a prerequisite for NLO molecules. 

Resorcinol (1,3-dihydroxybenzene [CAS 108-46-3]) Corrosive acid and protein denaturant extremely Irritating upon direct contact severe burns result. May cause methemoglobinemia (see p 261). A sensitizer. Dermally well absorbed, See also phenol, p 302. 10 ppm - 1 0 White crystalline solid with a faint odor, May turn pink on contact with air. Vapor pressure Is 1 mm Hg at 108°C (226°F). Combustible,... 

Dihydroxy-9,10-anthraquinone, see Anthracene Dihydroxybenzaldehyde, see 2-Methylphenol Dihydroxybenzenes, see Phenol 3,3 -Dihydroxybenzidine, see Benzidine /V,/V-Dihydroxybenzidine, see Benzidine... 

DIHYDROXY BEXZENE DIACETATE see REAIOO DIHYDROXYBENZENE (OSH.A) see HIHOOO 3,3 -DIHYDROXYBENZIDINE see DMI400... 

Phenols may have more than one hydroxy group attached to the same benzene ring - for example, the three isomeric dihydroxybenzenes catechol (ortho-dihydroxy-benzene or 1,2-benzenediol), resorcinol (meta-dihydroxy-benzene or 1,3-benzenediol) and hydroquinone (para-dihydroxybenzene or 1,4-benzenediol) see Figure 25.3. 

Dihydroxy-9(10i/)-anthracenone 380—see also AnthraUn, Dithranol Dihydroxyanthraquinones, chemical shifts for, isotope effects on 345, 346 Dihydroxybenzenes—see also Benzenediols, 4-Chloro-l, 2/3-dihydroxybenzenes, Dihydroxyalkylbenzenes, Hydroxyphenols methylation of 308 synthesis of 408, 409, 411... 

A PLS study has been performed on a series of 99 1,5-substituted-3,4-dihydroxybenzenes as catechol D-methyl-transferase (COMT, EC 2.1.1.6) inhibitors (see Fig. 22.12). A set of 19 variables to characterize the inhibitors was considered. This is a typical situation where MLR would pick out a few variables which together are best correlated to the biological activity. However, there may be several good combinations of descriptors with similar statistical relevance. PLS gives a better feeling of the contribution of each of the variables considered. In this case, the best PLS model showed that inhibition activity is nonlinearly related to the size of the R5 substituent and greatly depends on the electronic nature of both Ri and R5 substituents. Electron-withdrawing substituents enhance activity. 

In Chart 2 are depicted various poly-valent donor building blocks such as thiols, secondary amines, phosphotyl imines and ylids which serve both the purposes of diversification and cleavage as well as of construction of the central core stmctures. Bidentate nucleophiles such as thioamides, thioureas, ureas, isothioureas, amidines, guanidines, 1,2-dihydroxybenzenes, 2-aminothiophenols and others (see Chart 2) were exclusively employed for the synthesis of the cores as exemplified in Chapter 3 and 4 (the indicated references refer to these examples)... 

TP and Ag + were found to react with 4-methoxyphenol and 3,5-dimethoxyphenol by 100% electron transfer (equation 2), whereas with TlOH the efficiency of electron transfer is only ca 75%. The ease of oxidation increases considerably in going from the neutral phenols to the phenolates even the weak oxidants Tl(OH)2 and Ag(OH)2 are able to oxidize the phenolates with 100% yield to give the corresponding phenoxyl radicals. In going from phenol to the dihydroxybenzenes the oxidizability increases hydroquinone and resorcinol are oxidized with 100% yield not only by TP but also by the weaker oxidant TlOH . Catechol forms a complex with Tl(II), which has the same structure as thaf produced by reaction of ortfjo-semiquinone radical with Tl or by reaction of ort/io-benzoquinone with XT . The rate constants for reaction of the Tl(II) and Ag(II) species are between 10 -10 M s (see Table 1). 

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