Phenol polyhydric

From the commercial point of view, polyhydric phenols such as di- and trihydroxybenzene compounds are less important than phenol. In addition to synthesis, they can also be recovered from low-temperature tars, especially from the pyrolysis of brown coal. 

Catechol (o-dihydroxybenzene) was first discovered by Hugo Reinsch in 1839, by distilling catechin, a tannin-like cotton colorant. Since it was produced by destructive distillation, it was originally called pyrocatechol. 

The methyl ether of catechol, guaiacol, is contained in beechwood tar catechol can be produced from it by distillation with hydrobromic add. 

Outdated methods for producing catechol are based on o-sulfonated or o-ha-logenated phenols. These phenol derivatives are hydrolyzed under pressure with alkali and the reaction product is extracted with a solvent such as ether. The crude catechol is then refined by distillation. 

By present routes, catechol arises as a co-product in the synthesis of hydroqui-none from phenol by oxidation with peracids. Catechol is used as an antioxidant, principally for turpentine oil and perfumes. For the latter application, especially in the USA, 4-tert-butylcatechol, obtained by butylation, is used. 

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Hoesch synthesis A variation of the Gattermann synthesis of hydroxy-aldehydes, this reaction has been widely applied to the synthesis of anthocyanidins. It consists of the condensation of polyhydric phenols with nitriles by the action of hydrochloric acid (with or without ZnCl2 as a catalyst). This gives an iminehydrochloride which on hydrolysis with water gives the hydroxy-ketone. 

The Hoesch Reaction is employed for the introduction of the - COR group into the aromatic ring of phenol or a phenolic ether, and usually proceeds particularly readily with polyhydric phenols. If an ethereal solution of resorcinol (I)... 

By the condensation of a nitrile with a phenol or phenol ether in the presence of zinc chloride and hydrogen chloride a hydroxyaryl- or alkoxyaryl-ketone is produced. The procedure is termed the Hoesch reaction and is clearly an extension of the Gattermann aldehyde reaction (Section IV,121). The reaction gives the best results with polyhydric phenols and their ethers with simple monohydric phenols the imino ester hydrochloride is frequently the sole product for example ... 

Polycarbonate is a polyester in which dihydric (or polyhydric) phenols are joined through carbonate linkages. The general-purpose type of polycarbonate is based on 2,2-bis(4 -hydroxybenzene)propane (bisphenol A) and has the general structure ... 

Polyhydric phenols with more than two hydroxy groups (ie, the three positional isomers of benzenetriol, the three isomeric benzenetetrols, benzenepentol [4270-96-6] and benzenehexol [608-80-0]) are discussed in this article. The benzenediols are catechol, resorcinol, and hydroquinone (see Hydroquinone, RESORCINOL, AND CATECHOL). 

Ethylenethiourea reacts to form monosulftde cross-links (117). A number of alternative curatives have been proposed to avoid use of ethylene thiourea. These iaclude polyhydric phenols (118), hydroxyphenyl and mercapto substituted tria2oles (119), thiolactams (120), thia2o1idinethiones as Vulkacit CRV (121), and alkanethioamides (122). Among these, Vulkacit CRV is the most widely used. An accelerator is ordinarily used ia combination with a retarder to control premature cross-linking. Tetramethylthiuram disulfide [137-26-8] is ordinarily used for this purpose when the accelerator is either ethylenethiourea [96-45-7] or a thia2o1idinethione. 

The most satisfactory derivatives for phenols that are of low molecular weight or monohydric are the benzoate esters. (Their acetate esters are generally liquids or low-melting solids.) Acetates are more useful for high molecular weight and polyhydric phenols. 

Like other alkaloids of this group, quinine forms molecular compounds with a variety of organic substances. With benzene and toluene it produces compounds of the formulae B. CgHg and B. C,Hg respectively, with phenol it gives the crystalline product B. CgHjOH, and similar combinations with polyhydric phenols, ethers, aldehydes and ketones are known. One of the most characteristic of these substances is cupreine-quinine, a combination of the two alkaloids, obtainable from cuprea bark, and at first regarded as a new alkaloid, and named homoquinine. ... 

Sodium A-methylanilide, xylene, HMPA, 60-120°, 70-95% yield. Methyl ethers of polyhydric phenols are cleaved to give the mono-phenol. Benzyl ethers are also cleaved. Halogenated phenols are not effectively cleaved, because of competing aromatic substitution. 

The activation of persulfates by various reductant viz. metals, oxidizable metals, metal complexes, salts of various oxyacid of sulfur, hydroxylamine, hydrazine, thiol, polyhydric phenols, etc. has been reported [36-38]. Bertlett and Colman [39] investigated the effect of methanol on the decomposition of persulfates and proposed the following mechanism. 

The hexoses that are the initial products of acid hydrolysis of sucrose (1) react at el vated temperature under the influence of acids to yield furfural derivatives (2). Thed condense, for example, with the phenols to yield triarylmethanes (3), these react furthei by oxidizing to yield colored quinoid derivatives (2, 4). Polyhydric phenols, e. g. resorj cinol, on the other hand, yield condensation products of Types 5 and 6 [2],... 

Mono- and polyhydric phenols and enols frequently form characteristically color complexes with Fe + ions [4, 28, 29]. Here monohydric phenols usually produ reddish-violet colors, while pyrocatechol derivatives yield green chelates [4]. Detecti< of acetone using Legal s test is based on the formation of an iron complex [4]. T same applies to the thioglycolic acid reaction of the German Pharmacopoeia (DAB [4, 30]. 

It has been established 25) that a firm, thermally reversible gel of poly (vinyl alcohol) can be formed by mixing it with polyhydric phenols, 1-naphthols, and dihydric naphthols. Monohydric phenols have no action. Compounds such as catechol, phloroglucinol, and 1-naphthol are typical gelling agents. 

In the case of polyhydric phenols the synthesis of the carboxylic acid can be carried out even in aqueous solution. 

The anthocyanins are glucosides of polyhydric phenols and phenol ethers having OH and phenyl as substituents in the pyran ring. These glucosides can be regarded as derived from three types of sugar-free anthocyanidins. 

The ketone synthesis of Houhen and Hoesch, which is based on the principle of the Gattermann reaction, proceeds very smoothly and gives very favourable results, especially in the case of polyhydric phenols. In this synthesis nitriles are used. Here it is the iminochlorides R—C=NH which are converted into ketimines and then into ketones, a... 

Houben-Hoesch synthesis orgchem Condensation of cyanides with polyhydric phenols in the presence of hydrogen chloride and zinc chloride to yield phenolic ketones. hit-ban harsh sin-tha-sas ... 

Dihydric and Polyhydric Phenols under Dihydric, Polyhydric Phenols Dusopropyl Methyl Phosphonate DIMP under Organophosphonates Dimethyl Acetamide under Amides Dimethyl Disulfide under Sulfides, Disulfides... 

The reacting species is a rather weak electrophile and, therefore, only particularly reactive aromatics are suitable substrates. Consequently, the reaction is restricted for polyhydric phenols and their ethers, and reactive heterocycles. With strong acidic systems, such as AICI3 in halogenated benzene solvents, alkylben-zenes can react at more elevated temperatures (>50°C). Trichloroacetonitrile works also well with nonactivated aromatics. The 12 chloroimine, the protonated nitrile (13), or the nitrile coordinated with the Lewis acid are possible involved electrophiles. 

Di-aldehydes can be obtained from some polyhydric phenols. Phenolic-ethers also react, as do hydroxy-aldehydes and hydroxy-acids. 

The phthaleins derived from di- or polyhydric phenols are all anhydrides formed by the elimination of water from two phenolic hydroxyls, attached to two different benzene rings. These anhydride phthaleins are known as pyronines, since they contain, like the pyrones, a six-membered oxygen-containing ring. 

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