Alcohols & Phenols (Class 12)

• Lower: Colourless Liquid

• Higher: Viscous Liq / Solid

• Characteristic smell

• Higher than Alkanes

• Trend: 1° > 2° > 3°

• Reason: Inter-H Bonding

• Branching ↑ ⇒ BP ↓

• C1-C3: Completely miscible

• Chain length ↑ ⇒ Sol. ↓

• Alkyl group is Hydrophobic

1° > 2° > 3°

• +I effect destabilizes

• Density < Water

Class 12 CBSE Chemistry Revision Guide

• Lower: Colourless liquids

• Higher: Viscous liquids / solids

• Characteristic smell

2. Boiling Point (BP)

• Higher than Alkanes/Haloalkanes

• Reason: Intermolecular H-bonding

• Trend: 1° > 2° > 3°

• Branching ↑ ⇒ H-bonding ↓ ⇒ BP ↓

3. Solubility in Water

• Lower (C1-C3): Completely miscible

• Chain length ↑ ⇒ Hydrophobic part ↑ ⇒ Sol. ↓

4. Density & Viscosity

• Density < Water (Exc: Glycerol)

• Mass ↑ / -OH groups ↑ ⇒ Viscosity ↑

5. Dipole & Acidity

• Polar molecules (O-H bond)

• Acidity: 1° > 2° > 3°

• +I effect destabilizes alkoxide ion

• Colourless crystalline solid

• Turns pink on air exposure (Oxidation)

2. Melting & Boiling Point

• Higher than Alcohols (similar mass)

• Reason: Strong H-bonding + Planar Ring

3. Solubility

• Slightly soluble in water

• (Hydrophobic Benzene ring effect)

• Highly soluble in Ether, Alcohol, Benzene

4. Acidity (Key Point!)

• Phenols > Alcohols

• Reason: Phenoxide ion resonance

5. Others

• Density > Water

• Shows Inter- & Intramolecular H-bonding

• Corrosive, toxic, phenolic smell

• Very weak electrolytes