What Is Phenol?
Phenol, an aromatic compound characterized by a hydroxy group attached to a benzene ring, is a solid, colorless crystal at room temperature with a distinct odor. Initially derived from coal tar, modern production primarily uses benzene through various chemical processes like sulfonation and chlorination. Due to its bactericidal properties, phenol is utilized in numerous applications but requires careful handling due to its corrosive and toxic nature.
Applications of Phenol
As a versatile chemical, phenol is fundamental in producing bisphenol A, phenolic and epoxy resins, polycarbonate resin, and nylon, among others. It’s also a key ingredient in dyes, surfactants, agricultural chemicals, and pharmaceuticals. Its bactericidal effect lends it to use as a disinfectant and antiseptic, while its sensory numbing effect aids in pain and itch relief.
Properties of Phenol
Phenol has a density of 1.07g/cm3, a melting point of 40.5°C, and a boiling point of 181.7°C. It dissolves well in organic solvents and is slightly soluble in water. The hydroxyl group in phenol is weakly acidic, distinguishing it from the alcohols and contributing to its unique chemical behavior.
Other Information on Phenol
1. Resonance Effects and Keto-enol Tautomerism of Phenol
The conjugate base of phenol, the phenoxide ion, is stabilized through resonance, making phenol weakly acidic with a pKa of 9.95. This acid dissociation constant is significantly higher than that of typical alcohols.
2. Reaction of Phenol
Phenol readily forms sodium phenoxide with sodium or sodium hydroxide and can undergo reactions to produce compounds like phenolphthalein and 2,4,6-tribromophenol. Its nitration yields picric acid, though a preliminary sulfonation step is required to prevent oxidation.
3. Detection of Phenol
Phenolic compounds can be detected using aqueous iron (III) chloride, which reacts to produce a reddish-purple iron phenol complex, indicating the presence of phenolic hydroxy groups.