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Physical Properties of Ethers

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Estimated time: 7 minutes
CBSE: Class 12

Key Points: Physical Properties of Ethers

  • Colourless liquids (except dimethyl ether and diethyl ether, which are gases).
  • Polar due to bent structure (like a water molecule).
  • Low boiling point due to the absence of H-bonding between ether molecules.
  • Slightly soluble in water due to H-bonding with water; more soluble in organic solvents.
  • Structure: O is sp³ hybridised; two sp³ orbitals form O–C sigma bonds; two sp³ orbitals have lone pairs.
Maharashtra State Board: Class 12

Key Points: Physical Properties of Ethers

  • Methods of preparation of ethers: Acid-catalysed dehydration of alcohols (conc. H₂SO₄, 443 K); catalytic dehydration (Al₂O₃, 250°C); Williamson synthesis (alkyl halide + sodium alkoxide, Sₙ2); reaction of alkyl halides with dry Ag₂O.
  • Preparation of Diethyl Ether (Simple Ether): From ethanol using conc. H₂SO₄ / H₃PO₄ at 413 K; or by Williamson's synthesis from C₂H₅ONa + BrCH₂CH₃ under heat.
  • Reactions of Diethyl Ether: O₂ (long contact) → peroxide; dil. H₂SO₄ → 2 C₂H₅OH; PCl₅ → C₂H₅OH + C₂H₅Cl; hot HI → C₂H₅I + C₂H₅OH; excess HI → 2 C₂H₅I.
  • Preparation of Anisole (Mixed Ether): CH₃Br + sodium phenoxide (C₆H₅ONa) → Methyl phenyl ether (Anisole) on heating.
  • Reactions of Anisole: HI (398 K) → phenol + CH₃I; Br₂/CH₃COOH → p-bromoanisole (major) + o-bromoanisole (minor); conc. HNO₃ + conc. H₂SO₄ → 4-nitroanisole (major) + 2-nitroanisole (minor); CH₃Cl/AlCl₃ → 4-methoxytoluene (major) + 2-methoxytoluene (minor); CH₃COCl/AlCl₃ → 4-methoxyacetophenone (major) + 2-methoxyacetophenone (minor).

Shaalaa.com | Alcohol, Phenol and Ether part 27 (Ether physical Properties)

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