Phenols – Definition
Phenols are aromatic organic compounds in which a hydroxyl group (–OH) is directly attached to a benzene ring or other aromatic system.
General Features
- Formula: Ar–OH (where Ar = aromatic ring).
- Basic Unit: The simplest phenol is just C₆H₅OH.
- Bonding: The –OH group interacts with the aromatic ring through resonance, making the ring more reactive.
Properties
- Physical: Phenols are usually crystalline solids or liquids with a characteristic antiseptic smell. They are soluble in water due to hydrogen bonding and have higher boiling points than hydrocarbons.
- Chemical: Phenols are weak acids, more acidic than alcohols. They easily undergo electrophilic substitution reactions at ortho and para positions due to the activating effect of the –OH group.
Examples
- Phenol (C₆H₅OH)
- Cresols (methyl phenols)
- Naphthols (OH group attached to naphthalene ring)
Uses
- In antiseptics and disinfectants (e.g., Dettol contains chloroxylenol).
- In the manufacture of plastics (like Bakelite), dyes, pharmaceuticals (like aspirin), and synthetic fibers.
In short: Phenols are aromatic compounds with –OH directly bonded to the benzene ring, showing distinctive physical and chemical properties and wide industrial importance.