Chapter 11: Alcohol, Phenols and Ethers

Complete notes for Chapter 11. Covers Classification, Nomenclature, Preparation of Alcohols (Methanol, Ethanol), Phenols, and Ethers. Reactions including Oxidation, Dehydration, and Distinction tests.

Alcohols

Alcohols: Hydroxyl group (-OH) attached to alkyl group. General formula R-OH.

Classification:
- Monohydric: One -OH. (Primary, Secondary, Tertiary).
- Polyhydric: Multiple -OH (e.g., Glycol, Glycerol).
Nomenclature: IUPAC suffix is '-ol'.

Preparation of Alcohols

Methanol (Wood Spirit)

From Water Gas: CO + 2H2 -> CH3OH (ZnO + Cr2O3 catalyst, 450°C, 200 atm).

Ethanol

Fermentation: Biochemical process by enzymes (Yeast).
- From Molasses: Sucrose -> Glucose + Fructose (Invertase) -> Ethanol (Zymase).
- From Starch: Starch -> Maltose (Diastase) -> Glucose (Maltase) -> Ethanol (Zymase).
- Optimum temp 25-35°C. Max conc 12% (14% kills yeast).
- Rectified Spirit: 95% Ethanol.
- Absolute Alcohol: 100% Ethanol (Chemical drying with CaO).
- Denaturing: Adding Methanol (10%) or Pyridine/Acetone to make unfit for drinking (Methylated Spirit).
Industrial: Hydration of Alkenes.

Reactions of Alcohols

C-O Bond Breakage (Nucleophilic Attack): Reactivity: 3° > 2° > 1°. e.g., With HX (Lucas Reagent), SOCl2.
O-H Bond Breakage (Electrophilic Attack): Reactivity: 1° > 2° > 3°. e.g., With Na (Forms Alkoxide), Esterification (with Carboxylic Acid).
Oxidation:
- 1° Alcohol -> Aldehyde -> Carboxylic Acid.
- 2° Alcohol -> Ketone.
- 3° Alcohol -> Resistant (Elimination to Alkene).
Dehydration: Conc. H2SO4. Gives Ethers (low temp, excess alcohol) or Alkenes (high temp).
Distinction Tests:
- Lucas Test: Distinguishes 1°, 2°, 3° alcohols. (3° oily layer immediate, 2° in 5-10 min, 1° on heating).
- Iodoform Test: Ethanol gives yellow ppt (Methanol does not).

Phenols (Carbolic Acid)

OH group attached to Benzene ring.

Preparation

Dow's Method: Chlorobenzene + NaOH (360°C, 150 atm) -> Sodium Phenoxide -> Phenol.
From Sodium Benzenesulphonate.

Properties

Acidity: More acidic than Alcohols (Resonance stabilization of Phenoxide ion) but less than Carboxylic Acids.

Reactions

Nitration: Dil. HNO3 (o/p-nitrophenol), Conc. HNO3 (Picric Acid - 2,4,6-trinitrophenol).
Sulphonation: o/p isomers.
Halogenation: Bromine water -> 2,4,6-Tribromophenol (White ppt).
Reaction with HCHO: Forms Bakelite (Polymer).

Ethers

General formula R-O-R.

Preparation: Williamson's Synthesis (R-X + RONa), Dehydration of Alcohols.
Reactivity: Chemically inert. React with HI (forms Alcohol + Alkyl Halide).

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Chapter 11

chemistry • intermediate 12th