Monohydric phenols

Moat phenols are crystalline solids notable exceptions are m-cresol and o-bromophenol. The monohydric phenols generally have characteristic odours. The solubihty in water increases with the number of hydroxl groups in the molecule. 

Acetates. The acetates of monohydric phenols are usually liquids, but those of di and tri-hydric phenols and also of many substituted phenols are frequently crystaUine sohds. They may be prepared with acetic anhydride as detailed under Amines, Section IV,100,7. 

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 ... 

In the case of low temperature tar, the aqueous Hquor that accompanies the cmde tar contains between 1 and 1.5% by weight of soluble tar acids, eg, phenol, cresols, and dihydroxybenzenes. Both for the sake of economics and effluent purification, it is necessary to recover these, usually by the Lurgi Phenosolvan process based on the selective extraction of the tar acids with butyl or isobutyl acetate. The recovered phenols are separated by fractional distillation into monohydroxybenzenes, mainly phenol and cresols, and dihydroxybenzenes, mainly (9-dihydroxybenzene (catechol), methyl (9-dihydtoxybenzene, (methyl catechol), and y -dihydroxybenzene (resorcinol). The monohydric phenol fraction is added to the cmde tar acids extracted from the tar for further refining, whereas the dihydric phenol fraction is incorporated in wood-preservation creosote or sold to adhesive manufacturers. Naphthalene Oils. Naphthalene is the principal component of coke-oven tats and the only component that can be concentrated to a reasonably high content on primary distillation. Naphthalene oils from coke-oven tars distilled in a modem pipe stiU generally contain 60—65% of naphthalene. They are further upgraded by a number of methods. 

Constitution. Comparison of the empirical formula of the three alkaloids, and the fact that jatrorrhizine and columbamine each stands to palmatine in the relation of a monohydric phenol to its methyl ether, makes it clear that the only difference between jatrorrhizine and columbamine must be in the position of the free hydroxyl group. The method by which this point was settled is described in dealing with the two tetrahydro-derivatives of these alkaloids (p. 291). The constitution of palmatine (XXV R = R = Me) is dealt with under tetrahydropalmatine, but it is still necessary to describe the complete synthesis of this alkaloid via oxypalmatine (XXVII) and tetrahydropalmatine. 

Hoesch reaction. In most cases, a Lewis acid is necessary zinc chloride is the most common. The reaction is generally useful only with phenols, phenolic ethers, and some reactive heterocyclic compounds (e.g., pyrrole), but it can be extended to aromatic amines by the use of BCls. Acylation in the case of amines is regioselectively ortho. Monohydric phenols, however, generally do not give ketones " but are attacked at the oxygen to produce imino esters. Many nitriles... 

Mono- and polyl dric phenols and enols frequently form characteristically colored complexes with Fe + ions [4, 28, 29]. Here monohydric phenols usually produce reddish-violet colors, while pyrocatechol derivatives yield green chelates [4]. Detection of acetone using Legal s test is based on the formation of an iron complex [4]. The same applies to the thioglycolic acid reaction of the German Pharmacopoeia (DAB 9) [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. 

Bisphenol A, whose official chemical name is 2,2-bis(4-hydroxyphenyl)propane, is a difunctional monomer with two reactive hydroxyl groups, as shown in Fig. 20,2. It polymerizes svith dicarbonyl organic monomers, such as phosgene or diphenyl carbonate, which are illustrated in Fig. 20.3. During polymerization, shown in Fig. 20.4, the hydroxyl groups of the bisphenol A deprotonate in the presence of a base. After deprotonation, the oxygen atoms on the bisphenol A residue form ester bonds with the dicarbonyl compounds. The polymerization process terminates when a monohydric phenol reacts with the growing chain end. 

Oxidation of phenols.1 The reagent oxidizes 1,2- and 1,4-dihydroxyphenols to the quinones in almost quantitative yield at 25° in methanol. 4-Alkylphenols are oxidized to 4-alkyl-4-methoxycyclohexadienones (mixed quinone ketals) in >90% yield. Monohydric phenols can be oxidized to p-quinone diketals on oxidation with 2 equiv. of the reagent in CH,OH at 25°. 

Dianisyltellurium oxide (DAT) is a mild and selective oxidant for quinone for-mation. Treatment of the A,A-di-n-propyldopamine (2) with DAT leads to the betaine (3), which is identical with the product of oxidation by the enzyme tyrosinase both of (2) and of the monohydric phenol A,A-dimethyltyramine. The implications and relevance to the mode of action of tyrosinases have been discussed. 

Lead Compounds Lead Compounds Tetraethyl Lead Lithium Magnesium Manganese Mercury Molybdenum Monohydric Phenols Monohydric Phenols Phenol... 

Phenol, Dimethyl Xylenols under Monohydric Phenols... 

Fluoro-l,l-dimethoxy-3-methylbut-2-ene reacts smoothly with a number of phenols. Monohydric phenols containing either electron-releasing or electron-withdrawing substituents afford satisfactory yields of 3-fluoro-2,2-dimethylchromenes. The regioselectivity of this synthon appears to parallel that described above (80JHC1377). 

Phenols —> o-Quinones.2 This nitroxide is comparable to Fremy s salt for oxidation of monohydric phenols to quinones, but yields are low with simple phenols. The final step in a recent synthesis of methoxatin (4, a cofactor for a bacterial methanol dehydrogenose) required oxidation of the phenolic ring of 2 to an o-quinone (3) and ester hydrolysis. The usual oxidant, Fremy s salt, is not useful for... 

The terminal R groups can be aromatic or aliphatic. Typically, they are derivatives of monohydric phenolic compounds including phenol and alkylated phenols, eg, /-butylphenol. In interfacial polymerization, bisphenol A and a monofunctional terminator are dissolved in aqueous caustic. Methylene chloride containing a phase-transfer catalyst is added. The two-phase system is stirred and phosgene is added. The bisphenol A salt reacts with the phosgene at the interface of the two solutions and the polymer "grows" into the methylene chloride. The sodium chloride by-product enters the aqueous phase. Chain length is controlled by the amount of monohydric terminator. The methylene chloride—polymer solution is separated from the aqueous brine-laden by-products. The facile separation of a pure polymer solution is the key to the interfacial process. The methylene chloride solvent is removed, and the polymer is isolated in the form of pellets, powder, or slurries. 

However, our discussion will be restricted to oxidation of simple alkylated monohydric phenols (2-methoxy-4-alkylphenols), serving as models for noncondensed lignin units. In creosol (I) one ortho position and the para position is blocked, and coupling occurs at the 0-carbon atom under the conditions used. Other coupling mechanisms could not be detected (Figure 7). 

The classical and the most useful laboratory method for the preparation of quinones is the oxidation of monohydric phenols with the radical reagent, potassium nitrosodisulphonate [(K03S)2NO] (Fremy s salt) (the Teuber reaction).5 Details for the conversion of 3,4-dimethylphenol into 3,4-dimethyl-1,2-benzoquinone may be regarded as typical55 the probable mechanistic pathway is formulated below. 

Concentrated sulphuric acid is generally used as the condensing agent for simple monohydric phenols and /J-ketoesters, although phenol itself reacts better in the presence of aluminium chloride (Expt 8.45). The mechanism of the reaction is thought to involve the initial formation of a -hydroxy ester, which then cyclises and dehydrates to yield the coumarin. 

This second phase of the inhibition mechanism, which is proved by the isolation of a similar peroxide with quinol structure from monohydric phenols (13,15) is unfavorably affected by steric influence of the present substituent R however, even physical factors will probably influence the activity—e.g., the change in the solubility of the antioxidant in the substrate caused by substitution. The possible resonance of radical VUIb is also illustrated in the scheme. In this case the second radical R OO may be fixed in position 5 (IXb). The reaction may be used to help... 

Therefore, additional heat aging tests were conducted to investigate the possibility that hydroquinone-derived phenolic groups might function differently from the monohydric phenols and somehow contribute to the high activity of the phenolic-phosphite systems. Two substituted hydro-quinones, two polymeric phenolic phosphites based on those hydro-quinones, and combinations of the hydroquinones with triphenyl phosphite and tris(nonylphenyl) phosphite were evaluated in the oven-aging test again 0.4% DLTDP was included in the formulations. 

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