Phenol

• BPPhenol
• JPPhenol
• Ph. Eur.Phenol
• USP–NFPhenol

Benzenol; carbolic acid; hydroxybenzene; monohydroxybenzene; phenic acid; phenolum; phenylic acid

Phenol · [108-95-2]

UNII 339NCG44TV · PubChem CID 996

C6H6O · 94.11

Antimicrobial preservative

Typical concentrations: ≈0.5% injections · Dosage forms: Sterile (parenteral/ophthalmic)

Used mainly as an antimicrobial preservative in parenteral products, typically at about 0.25–0.5% w/v, including some insulin preparations and vaccines; it is also used in some topical and oral preparations such as mouthwashes and throat sprays. At higher concentrations phenol is used as a disinfectant, and in topical products it has antipruritic and mild local anaesthetic effects. Its antimicrobial action is bactericidal at about 1% and bacteriostatic at lower concentrations.

Colourless to faintly pink, hygroscopic crystals or a crystalline mass with a characteristic, aromatic odour. It liquefies readily when a small amount of water is added; liquefied phenol contains about 10% water.

Melting point

about 41 °C

Boiling point

about 182 °C

pKa

about 10.0 (25 °C)

Density

about 1.07 g/cm³

Solubility

soluble in water (about 1 in 15); very soluble in ethanol, glycerol, chloroform and ether; soluble in fixed and volatile oils

Phenol darkens to pink or red on exposure to air and light, a change accelerated by alkalinity and traces of metals such as iron and copper. Aqueous solutions are stable. Store in an airtight, light-resistant container in a cool place.

Precipitates albumin and gelatin, and gives coloured complexes with ferric salts. It forms liquid or soft eutectic mixtures with compounds such as camphor, menthol, thymol, phenazone and salol. Its preservative activity is reduced by nonionic surfactants and at alkaline pH; it is also incompatible with strong oxidising agents.

Originally isolated from coal tar, phenol is now made mostly synthetically, chiefly by the cumene process, in which cumene hydroperoxide is cleaved with acid to give phenol and acetone.

Concentrated phenol is corrosive to skin and mucous membranes and is rapidly absorbed through the skin, lungs and gut; systemic poisoning can affect the central nervous system, heart and kidneys. At the low concentrations used as a preservative it is generally well tolerated, although local irritation and rare hypersensitivity reactions have been reported.

Phenol is toxic and corrosive. Wear chemical-resistant gloves, eye protection and protective clothing, and handle in a fume cupboard or with good ventilation. Skin contact should be washed off immediately with plenty of water or with polyethylene glycol.

Included in the FDA Inactive Ingredient Database (injections; oral, topical and other preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Chlorocresol; cresol; liquefied phenol; thymol.

Phenol is more effective against bacteria than against fungi and spores. Its activity is strongly pH dependent because only the un-ionised form is active, and it is lost from solution by sorption into rubber closures and some plastics, which should be considered in container selection.