Numford
Organic conversion

Ethanol to methanamine

3 steps: oxidation, then condensation, then Hoffmann bromamide degradation

Class 12, Chapter 7 Alcohols, Phenols and Ethers; Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids; Class 12, Chapter 9 Amines

  1. OH
    EthanolCH₃CH₂OHAlcohol
  2. Step 1

    KMnO₄, KOH, heat; then H₃O⁺

    i

    Alkaline KMnO₄ oxidises a primary alcohol all the way to the acid.

    Also written: K₂Cr₂O₇, H₂SO₄

    OOH
    Ethanoic acidCH₃COOHCarboxylic acid
  3. Step 2

    NH₃, then heat

    i

    The acid first forms ammonium ethanoate, which loses water on heating.

    OH2N
    EthanamideCH₃CONH₂Amide
  4. Step 3

    Br₂ + NaOH(aq)

    Hoffmann bromamide degradation
    i

    Hoffmann bromamide degradation: the amine has one carbon less than the amide.

    NH2
    MethanamineCH₃NH₂Amine

Exam answer

  1. Step 1: Ethanol to ethanoic acid: KMnO₄, KOH, heat; then H₃O⁺.
  2. Step 2: Ethanoic acid to ethanamide: NH₃, then heat.
  3. Step 3: Ethanamide to methanamine: Br₂ + NaOH(aq).
Alternative routes (3)
  • Ethanol → Ethanal → Ethanoic acid → Ethanamide → Methanamine
    1. Ethanol to ethanal: PCC.
    2. Ethanal to ethanoic acid: KMnO₄, dilute H₂SO₄.
    3. Ethanoic acid to ethanamide: NH₃, then heat.
    4. Ethanamide to methanamine: Br₂ + NaOH(aq).
  • Ethanol → Ethanoic acid → Ethanoyl chloride → Ethanamide → Methanamine
    1. Ethanol to ethanoic acid: KMnO₄, KOH, heat; then H₃O⁺.
    2. Ethanoic acid to ethanoyl chloride: SOCl₂.
    3. Ethanoyl chloride to ethanamide: NH₃.
    4. Ethanamide to methanamine: Br₂ + NaOH(aq).
  • Ethanol → Ethanoic acid → Ethanoic anhydride → Ethanamide → Methanamine
    1. Ethanol to ethanoic acid: KMnO₄, KOH, heat; then H₃O⁺.
    2. Ethanoic acid to ethanoic anhydride: conc. H₂SO₄ (or P₂O₅), heat.
    3. Ethanoic anhydride to ethanamide: NH₃.
    4. Ethanamide to methanamine: Br₂ + NaOH(aq).
Why these reagents

Reagent and reason, step by step

  • Step 1: Ethanol to ethanoic acid: KMnO₄, KOH, heat; then H₃O⁺ Alkaline KMnO₄ oxidises a primary alcohol all the way to the acid.
  • Step 2: Ethanoic acid to ethanamide: NH₃, then heat The acid first forms ammonium ethanoate, which loses water on heating.
  • Step 3: Ethanamide to methanamine: Br₂ + NaOH(aq) Hoffmann bromamide degradation: the amine has one carbon less than the amide.
Questions

Ethanol to methanamine: quick answers

How many steps does it take to convert ethanol to methanamine?

3 steps: Ethanol, then ethanoic acid, then ethanamide, then methanamine.

Which named reaction is used to convert ethanol to methanamine?

Hoffmann bromamide degradation. An amide treated with bromine and aqueous or alcoholic NaOH gives a primary amine with one carbon atom fewer.

What is the reagent for step 1 of ethanol to methanamine?

Ethanol to ethanoic acid: KMnO₄, KOH, heat; then H₃O⁺. Alkaline KMnO₄ oxidises a primary alcohol all the way to the acid.

Plan your own conversion