Alcohols, Phenols and Ethers

Notes

1. Introduction Organic compounds containing oxygen are mainly classified into: Compound Functional Group General Formula Alcohol –OH attached to sp³ carbon R–OH Phenol –OH attached directly to benzene ring Ar–OH Ether Oxygen between two carbon atoms R–O–R' 2. Classification of Alcohols (A) Based on Number of –OH Groups Monohydric → One –OH Dihydric → Two –OH Trihydric → Three –OH Example: CH₃OH → Monohydric HO–CH₂–CH₂–OH → Dihydric Glycerol → Trihydric (B) Based on Carbon Attached to –OH Primary (1°) R–CH₂OH Example: CH₃CH₂OH Secondary (2°) R₂CHOH Example: CH₃CHOHCH₃ Tertiary (3°) R₃COH Example: (CH₃)₃COH 3. Nomenclature Alcohol Replace -e of alkane by -ol Examples CH₃OH → Methanol CH₃CH₂OH → Ethanol CH₃CHOHCH₃ → Propan-2-ol Ether Name alkoxy + alkane CH₃OCH₃ Methoxy methane Phenol C₆H₅OH Phenol 4. Preparation of Alcohols (i) From Haloalkanes RX + KOH(aq) ↓ ROH (ii) Hydration of Alkenes CH₂=CH₂ + H₂O H⁺ ↓ CH₃CH₂OH (iii) Reduction of Carbonyl Compounds Aldehyde → Primary alcohol Ketone → Secondary alcohol Reducing agents NaBH₄ LiAlH₄ H₂/Ni (iv) Grignard Reagent RMgX + Carbonyl compound ↓ Alcohol after hydrolysis 5. Preparation of Phenol From Chlorobenzene Dow's Process C₆H₅Cl NaOH 623 K ↓ C₆H₅OH From Benzene Diazonium Chloride C₆H₅N₂⁺Cl⁻ Warm water ↓ Phenol Cumene Process Cumene ↓ Cumene hydroperoxide ↓ Phenol + Acetone (Board Favourite) 6. Preparation of Ether Williamson Ether Synthesis RONa + R–X ↓ ROR + NaX Best for Primary Haloalkanes 7. Physical Properties Alcohols ✔ Hydrogen bonding present Hence High boiling point Water soluble (lower alcohols) Boiling point order Alcohol > Ether > Alkane Phenol Less soluble than alcohol High boiling point Ether No intermolecular hydrogen bonding Low boiling point Slightly soluble in water 8. Acidic Nature Alcohol Very weak acid ROH + Na ↓ RONa + H₂ Phenol More acidic than alcohol because Phenoxide ion is resonance stabilized. Order Phenol > Alcohol Electron withdrawing groups increase acidity. Electron donating groups decrease acidity. 9. Chemical Reactions of Alcohols (i) Reaction with Sodium ROH…