NEET Chemistry Notes Alcohols,Phenols and ethers -Phenols

NEET Chemistry Notes Alcohols,Phenols and ethers -Phenols

Phenols

Phenols (C₆H₅OH)

Aromatic compounds in which hydroxyl group (— OH) is directly attached with benzene nucleus are called phenols.

Preparation

Some general and important methods of preparation of phenols are discussed below:

Physical Properties of Phenols

Phenol has higher boiling point and soluble in water due to its ability to form hydrogen bond with water.

Acidic Nature of Phenol

Phenols are acidic in nature, even more acidic than alcohols. The more acidic character of phenols (than corresponding aliphatic alcohols) is due to conjugation between lone pair of oxygen and benzene nucleus, i.e.

The positive charge on oxygen signifies the weakening of O—H bond. Presence of electron releasing group like —CH₃, —C₂H₅ over benzene nucleus destabilises the phenoxide ion, thus, decreases the acidity of phenol whereas, presence of electron withdrawing groups like —N0₂, —CN, etc,, stabilises the phenoxide ion and thus, increases the acidity of phenol.

Chemical Properties of Phenols
Phenols exhibit the following chemical properties.

Electrophilic Substitution Reactions

In phenol, the—OH group shows +R and -I effect and hence, highly activates the benzene ring towards electrophilic substitution reaction. It is ortho and para directing group.

Nitration

The ortho and para isomers can be separated by steam distillation, o-nitrophenol is steam volatile due to intramolecular hydrogen bonding while p-nitrophenol is less volatile due to intermolecular hydrogen bonding.

 Halogenation

Kolbe’s Reaction

Reimer-Tiemann Reaction

Reactions Involving Breaking of O—H Bond

Both the above reactions show acidic nature of phenol.

Oxidation

Uses

1. Phenol is used in the manufacture of bakelite, soaps, lotions, etc.
2. It is used in the manufacture of drugs like aspirin, salol, phenacetin, etc.

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