Class 12th Chemistry Alcohols, Phenols, and Ethers Notes

🍃 1. Alcohols (Functional Group -OH) 💧

Structure and Functional Group:

• Alcohols contain a hydroxyl group (-OH) attached to a saturated carbon atom.
• General formula: R-OH.

Preparation of Alcohols:

• Hydration of Alkenes:
  • Alkene + H₂O (acid catalyst) → Alcohol.
  • Example: Ethene → Ethanol.
• Reduction of Carbonyl Compounds:
  • Aldehydes and ketones can be reduced using reducing agents like NaBH₄ to form alcohols.
• Fermentation:
  • Glucose → Ethanol + CO₂ (in the presence of yeast).

Chemical Properties of Alcohols:

• Oxidation:
  • Primary alcohols → Aldehydes → Carboxylic acids.
  • Secondary alcohols → Ketones.
  • Tertiary alcohols do not undergo oxidation.
• Dehydration:
  • Alcohols undergo dehydration to form alkenes in the presence of an acid catalyst.

Uses of Alcohols:

• Solvents:
  • Ethanol is widely used as a solvent in medicines, perfumes, and paints.
• Fuel:
  • Ethanol is used as a biofuel in internal combustion engines.
• Disinfectants:
  • Isopropyl alcohol is used as an antiseptic and disinfectant.

🌿 2. Phenols (Functional Group -OH attached to an aromatic ring) 🌺

Structure and Functional Group:

• Phenols have a hydroxyl group (-OH) attached to a benzene ring.
• General formula: C₆H₅OH.

Preparation of Phenols:

• From Chlorobenzene:
  • Chlorobenzene + NaOH → Phenol + NaCl (High temperature).
• From Cumene (Isopropylbenzene):
  • Cumene hydroperoxide → Phenol + Acetone.

Acidity of Phenols:

• Phenols are more acidic than alcohols due to the ability of the phenoxide ion (C₆H₅O⁻) to stabilize the negative charge by resonance with the benzene ring.

Chemical Reactions of Phenols:

• Electrophilic Substitution:
  • Phenols react with electrophiles such as bromine to form bromophenols.
• Oxidation:
  • Phenols can be oxidized to form quinones.

Uses of Phenols:

• Antiseptics:
  • Phenol (Carbolic acid) is used as an antiseptic in medical applications.
• Antioxidants:
  • Phenols like butylated hydroxyToluene (BHT) are used as preservatives in food.
• Disinfectants:
  • Chloroxylenol, a phenol derivative, is used in detergents and disinfectants.

🌸 3. Ethers (Functional Group -O-) 🌼

Structure and Functional Group:

• Ethers contain an oxygen atom bonded to two alkyl or aryl groups.
• General formula: R-O-R’.

Preparation of Ethers:

• From Alcohols:
  • Dehydration of alcohols in the presence of an acid catalyst.
  • Example: 2 Ethanol → Diethyl ether.
• From Alkyl Halides:
  • Alkyl halide + Alkoxide ion (RO⁻) → Ether.

Chemical Reactions of Ethers:

• Reaction with Acid:
  • Ethers react with strong acids to break the C-O bond, forming alcohols or alkyl halides.
• Reaction with Halogens:
  • Ethers undergo halogenation in the presence of light to form alkyl halides.

Uses of Ethers:

• Solvents:
  • Ethers like diethyl ether are used as solvents in laboratories and pharmaceutical preparations.
• Anesthetics:
  • Ether (Ethoxyethane) was historically used as a general anesthetic.
• In Pharmaceuticals:
  • Ethers are used in the synthesis of medicines and pharmaceutical products.

💧 Conclusion 🧪

• Alcohols, phenols, and ethers are important functional groups in organic chemistry, each with its own unique preparation methods, chemical properties, and industrial applications.
• Alcohols are widely used in solvents, phenols serve as antiseptics and antioxidants, while ethers are essential solvents and have applications in anesthesia and pharmaceuticals.

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