phenol

phenol

(fē`nōl), C₆H₅OH, a colorless, crystalline solid that melts at about 41°C;, boils at 182°C;, and is soluble in ethanol and ether and somewhat soluble in water. An aromatic alcohol, it exhibits weak acidic properties and is corrosive and poisonous. Phenol is sometimes called carbolic acid, especially when in water solution. It reacts with strong bases to form salts called phenolates. Phenol is important in industry in the production of certain artificial resins, e.g., Bakelite, and in the synthesis of many drugs, dyes, weed killers, insecticides, and explosives (e.g., picric acid). It is the simplest member of a class of hydroxy benzene derivatives, all of which contain a hydroxyl group attached to a benzene ring; these compounds may be thought of as derivatives of phenol and generically are called phenols.

Phenol

 

(also hydroxybenzene, carbolic acid), a colorless crystalline compound with a characteristic odor. Phenol turns pink upon storage. It has a melting point of 40.9°C and a boiling point of 181.75°C. The compound is moderately soluble in water and readily soluble in alcohol, ether, and acetone. The structural formula is

Phenol is the simplest of the hydroxyl derivatives of aromatic hydrocarbons and is an important raw material for a number of valuable products. Thus, the industrial chlorination of phenol with elemental chlorine yields 2,4-dichlorophenol, an intermediate in the production of 2,4-dichlorophenoxyacetic acid. The condensation of phenol with aldehydes, principally formaldehyde, yields phenol-aldehyde resins. Condensation with phthalic anhydride yields phenolphthalein (an indicator and drug), and condensation with acetone produces diphenylolpropane, which is used in producing polycarbonates. The hydrogenation of phenol produces cyclohexanol, an intermediate in the synthesis of capro-lactam (the polymerization of which yields polycaproamide), while the compound’s alkylation with olefins produces n-alkyl phenols (RC₆H₄OH), which are used in the manufacture of surfactants and odoriferous substances. Phenol is also used in the production of picric acid and of various dyes and drugs (salicylic acid, phenyl salicylate).

Phenol can be isolated from coal tar. It is obtained synthetically from benzene through benzenesulfonic acid (C₆H₅SO₂OH) in a process involving the fusion of the acid’s sodium salt with sodium hydroxide. The compound can also be obtained synthetically from chlorobenzene (C₆H₅Cl) through hydration, but the principal synthetic method involves the breakdown of cumene hydroperoxide.

Phenol is bactericidal. In medicine, where it is better known as carbolic acid, it is used in the form of diluted aqueous solutions to disinfect hospital rooms and equipment. Phenol burns upon contact with the skin. The maximum permissible concentration of phenol in the air is 0.005 mg per liter.

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Phenol

 

any of the hydroxyl derivatives of aromatic compounds containing one or more hydroxyl groups (—OH) bonded to the aromatic ring. The number of OH groups determines whether the phenol is monohydric, dihydric, or polyhydric. Monohydric phenols include hydroxybenzene (C₆H₅OH), which is usually referred to simply as phenol, hydroxytoluenes (cresols, CH₃C₆H₄OH), and hydroxynaphthalenes (naphthols). An example of a dihydric phenol is dihydroxybenzene [C₆H₄(OH)₂: hydroquinone, pyrocatechol, and resorcinol]. Polyhydric phenols include pyrogallol and phloroglucinol.

Phenols are colorless crystalline compounds with a characteristic odor; less frequently, they occur as liquids. They are readily soluble in such organic solvents as alcohol, diethyl ether, and benzene. Possessing acid properties, phenols form saltlike products known as phenolates: ArOH + NaOH ⇄ ArONa + H₂O (Ar representing an aromatic radical). Alkylation or acylation of phenolates yields ethers (ArOR) and esters (ArOCOR) of phenols, respectively (R being an organic radical). Esters of phenols may be obtained by the direct reaction of phenols with carboxylic acids and with the acids’ anhydrides and acid chlorides. Upon heating, phenols react with CO₂ to yield phenolic acids, such as salicylic acid. In contrast to alcohols, the hydroxyl groups of phenols are replaced by halogens only with great difficulty. Electro-philic substitution in the phenol ring (halogenation, nitration, sulfonation, alkylation) occurs much more readily than in unsubstituted aromatic hydrocarbons; here, the substituting groups are directed to positions that are ortho and para relative to the OH group. The catalytic hydrogenation of phenols yields alicyclic alcohols; C₆H₅OH, for example, is reduced to cyclohexanol. Condensation reactions, such as those with aldehydes and ketones, are typical of phenols; this feature is used in industry in producing phenol-formaldehyde resins, phenolic resins using resorcinol, and diphenylolpropane.

Phenols are produced by, among other methods, the hydrolysis of the corresponding halogen derivatives and the alkaline fusion of arylsulfonic acids (ArSO₂OH). They are also obtained by separation from coal tar. Phenols are important raw materials in the production of plastics, adhesives, paints, varnishes, dyes, drugs (phenolphthalein, salicylic acid, phenyl salicylate), surfactants, and odoriferous substances. Certain phenols are used as antiseptics and antioxidants (of polymers, lubricants). Solutions of iron chloride, which reacts with phenols to form colored products, are used for qualitative determination of phenols. Phenols are toxic.

REFERENCE

Nesmeianov, A. N., and N. A. Nesmeianov. Nachala organicheskoi khimii, vol. 2,2nd ed. Moscow, 1974.

phenol

[′fē‚nȯl]

(organic chemistry)

C₆H₅OH White, poisonous, corrosive crystals with sharp, burning taste; melts at 43°C, boils at 182°C; soluble in alcohol, water, ether, carbon disulfide, and other solvents; used to make resins and weed killers, and as a solvent and chemical intermediate. Also known as carbolic acid; phenylic acid.

A chemical compound based on the substitution product of phenol, for example, ethylphenol (C₂H₄C₄H₅OH), the ethyl substitute of phenol.

phenol

A class of acid organic compounds used in the manufacture of epoxy resins, phenol-formaldehyde resins, plasticizers, plastics, and wood preservatives.

phenol

1. a white crystalline soluble poisonous acidic derivative of benzene, used as an antiseptic and disinfectant and in the manufacture of resins, nylon, dyes, explosives, and pharmaceuticals; hydroxybenzene. Formula: C₆H₅OH

2. Chem any of a class of weakly acidic organic compounds whose molecules contain one or more hydroxyl groups bound directly to a carbon atom in an aromatic ring