Convert, acetamide into ethyl amine.(ii) Explain amphoteric nature of water.

Answer:

(i) Acetamide is reduced by lithium aluminium hydride in dry ether, followed by hydrolysis; the C=O group becomes CH₂ and the carbon chain is kept:

CH₃CONH₂ + 4[H] —(LiAlH₄, dry ether; then H₂O)→ CH₃CH₂NH₂ (ethylamine) + H₂O

(Hofmann bromamide degradation would remove one carbon and give methylamine, so reduction is used here.)

(ii) Amphoteric nature of water: A substance that can act both as a Brønsted acid (proton donor) and a Brønsted base (proton acceptor) is amphoteric. Water is amphoteric:

• With an acid such as HCl, water accepts a proton and acts as a base: H₂O + HCl → H₃O⁺ + Cl⁻
• With a base such as NH₃, water donates a proton and acts as an acid: H₂O + NH₃ ⇌ NH₄⁺ + OH⁻
• Water also self-ionises: H₂O + H₂O ⇌ H₃O⁺ + OH⁻, one molecule acting as acid and the other as base.