Phenolic ethers mineral acids

A A Dimethylamino)phenol. 3-Hydroxy-A7,A7-dimethylariiline (14) forms white needles and is soluble in alkaU, mineral acid, ethanol, diethyl ether, acetone, and benzene and practically insoluble in water. 

The ethers of the phenols are very stable substances in which the reactivity of the benzene ring, as compared with that of the phenols themselves, is appreciably reduced. The alkyl group is very firmly attached. It cannot be removed by the action of alkalis, and by that of mineral acids only at high temperature (in sealed tubes). The most useful agent for reconverting phenolic ethers into phenols is aluminium chloride, which acts in the manner shown in the following equation ... 

Properties Reddish or yellowish oil becomes brownish on exposure to air, volatile with steam. D 1.097 (20C), bp 225C, fp 5C. Soluble in dilute mineral acid, alcohol, and ether insoluble in water. Derivation (1) Reduction of o-mtroamsole with tin or iron and hydrochloric acid (2) heating o-amino-phenol with potassium methyl sulfate. 

The preparation of / -diiodobenzene given as an example above showed that iodine can be very easily substituted for a diazonium group by means of hydriodic acid without addition of a copper(i) salt. A little urea is added to the diazotized solution (to remove residual HN02), which is usually prepared in hydrochloric or sulfuric acid, followed by a cold iodide solution (1-2 moles of alkali iodide per mole of diazotized amine) or the solution of the diazonium salt in mineral acid is added to a cold iodide solution. Evolution of nitrogen ceases after storage for several hours or, if necessary, subsequent warming on a wather-bath. Phenols can be expected as by-products and may be removed by basification before isolation of the aryl iodide the latter is obtained then by distillation in steam, extraction in ether, CHC13, benzene, or toluene, or filtration. Biaryls and azo compounds are not formed, because the mechanism... 

Reaction of phenols and olefins may lead to ether formation and to nuclear alkylation catalysts are mineral acids, sulfonic acids, or boron trifluoride. Ethers are formed at lower temperatures, C-alkylation occurs by rearrangement at higher temperatures.156,157... 

Alcohols. Methanol and ethanol have long been important alkylating agents, especially for nitrogen bonding. In practically every case, a catalyst is necessary to cause the alkylation to proceed smoothlyvand in many instances, this is a mineral acid. Alcohols are used in the manufacture of ethers, such as ordinary ethyl ether, isopropyl ether, Carbitol, Cellosolve, and naphthyl methyl ether. It should be noted that, although naphthols react with alcohol in the presence of a mineral acid, the aryl alkyl ethers cannot be formed by this reaction in the case of phenols. 

Pyrolysis of tri-, tetra-, and penta-chlorobenzenes affords mixtures of chlorinated dibenzofurans and dibenzo-p-dioxins, " and chlorinated diphenyl ethers cyclize in the presence of palladium acetate to polychloro-dibenzofurans/ The action of malononitrile on tetrahydroxy-p-benzoquinone leads to the benzo-difuran (79), contrary to a previous report/ The acid-catalysed condensation of quinones with phenols has been studied p-benzoquinone and resorcinol, for example, afford compound (80)/ Naphtho[2,3- >]furan-4,9-diones (81 R = Me or Ph R = Ac, Bz, C02Et, or CN) are obtained from 2,3-dichloronaphtho-1,4-quinone and compounds R COCHaR in DMF that contains potassium fluoride/ The action of mineral acids on p-benzoquinone produces a mixture of complex benzofurans, which includes (82) and (83)/ Bases convert the ben-zofuranone (84) into the tetrameric compound (85), contrary to an earlier... 

Dubach and Mehta (1963) define humic substances as a series of predominantly aromatic-phenolic polymers, whose acidity is mainly due to carboxyl groups, and which are free of carbohydrates and probably of nitrogen. They state that the presence of quinonic structures cannot be confirmed or excluded. They are of the opinion that there are ether linkages between the aromatic monomers, but humic substances are too nonhomogeneous to justify an attempt to write a structural formula for them, as was done in the past. The humic substances constitute over 50% of the organic matter of mineral soils. At the present time few workers would have any doubt that these substances contain nitrogen. 

Weakly acidic phenols that do not react with diazomethane can be methylated with sodium hydride and methyl iodide in THF at room temperature. The methoxymethyl ether moiety can be used to protect phenols. It is stable to alkali, Grignard reagents, lithium aluminum hydride, and catalytic hydrogenation, and is readily removed by mineral acid. Dimethoxymethane can be used in lieu of the carcinogenic chloromethyl methyl ether for this purpose. Alternatively, phenols may be protected as methyl thiomethyl ethers.The (9-acetylation of phenols in the presence of primary and secondary amines can be carried out with acetyl bromide and TFA. ... 

Propylene oxide and 1,2-butylene oxide cyclic ethers find their largest use as chemical intermediates. Both oxides react readily with dilute amounts of mineral acids (e.g., hydrochloric acid) to form the chlorohydrin addition product. This reactivity with acid make these epoxy solvents valuable acid acceptor-type stabilizers for several chlorinated solvents. Trace amounts of hydrogen chloride from chlorinated solvent degradation is immediately neutralized by reaction with the propylene or 1,2-butylene oxide stabilizer. Reaction of propylene oxide with an alcohol or phenol in the presence of an acid catalyst yields the monoether of propylene glycol (see Chapter 13 for the glycol ethers). 

Thin-layer analysis of the hydrolysates requires removal of the mineral acid used for hydrolysis. Ion exchange resins are widely used, but some classical procedures are also very useful. After hydrolysis with 1 M sulfuric acid, the acid may be removed as barium sulfate by adding barium carbonate solution. Small amounts of 1 M hydrochloric acid can be removed in vacuo, and larger amounts of this acid can be conveniently removed from an aqueous hydrolysate by repeated washing with a 10% solution of di-n-octylmethylamine in chloroform etc. The hydrolysates plant of plant glycosides usually contain interfering compounds such as phenolics. These can be removed by extracting the hydrolysates with diethyl ether or ethyl acetate (26). 

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