Numford
Organic conversion

Chloroethane to propanoic acid

2 steps: substitution, then hydrolysis

Class 12, Chapter 6 Haloalkanes and Haloarenes; Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids

  1. Cl
    ChloroethaneCH₃CH₂ClHaloalkane
  2. Step 1

    KCN (alcoholic)

    i

    KCN attacks through carbon, adding one carbon.

    N
    PropanenitrileCH₃CH₂CNNitrile
  3. Step 2

    H₃O⁺, heat

    i

    Complete hydrolysis goes through the amide to the acid.

    OHO
    Propanoic acidCH₃CH₂COOHCarboxylic acid

Exam answer

  1. Step 1: Chloroethane to propanenitrile: KCN (alcoholic).
  2. Step 2: Propanenitrile to propanoic acid: H₃O⁺, heat.
Alternative routes (4)
  • Chloroethane → Propanenitrile → Propanal → Propanoic acid
    1. Chloroethane to propanenitrile: KCN (alcoholic).
    2. Propanenitrile to propanal: (i) SnCl₂ + HCl (ii) H₃O⁺.
    3. Propanal to propanoic acid: KMnO₄, dilute H₂SO₄.
  • Chloroethane → Propanenitrile → Propanamide → Propanoic acid
    1. Chloroethane to propanenitrile: KCN (alcoholic).
    2. Propanenitrile to propanamide: dilute acid, mild conditions (partial hydrolysis).
    3. Propanamide to propanoic acid: H₃O⁺, heat.
  • Chloroethane → Ethene → Bromoethane → Propanenitrile → Propanoic acid
    1. Chloroethane to ethene: alc. KOH, heat.
    2. Ethene to bromoethane: HBr.
    3. Bromoethane to propanenitrile: KCN (alcoholic).
    4. Propanenitrile to propanoic acid: H₃O⁺, heat.
  • Chloroethane → Ethene → Bromoethane → Ethylmagnesium bromide → Propanoic acid
    1. Chloroethane to ethene: alc. KOH, heat.
    2. Ethene to bromoethane: HBr.
    3. Bromoethane to ethylmagnesium bromide: Mg, dry ether.
    4. Ethylmagnesium bromide to propanoic acid: (i) CO₂ (dry ice), dry ether (ii) H₃O⁺.
Why these reagents

Reagent and reason, step by step

  • Step 1: Chloroethane to propanenitrile: KCN (alcoholic) KCN attacks through carbon, adding one carbon.
  • Step 2: Propanenitrile to propanoic acid: H₃O⁺, heat Complete hydrolysis goes through the amide to the acid.
Questions

Chloroethane to propanoic acid: quick answers

How many steps does it take to convert chloroethane to propanoic acid?

2 steps: Chloroethane, then propanenitrile, then propanoic acid.

Which named reaction is used to convert chloroethane to propanoic acid?

None of the steps has a name. They are substitution and hydrolysis, so write the reagent and the condition for each step.

What is the reagent for step 1 of chloroethane to propanoic acid?

Chloroethane to propanenitrile: KCN (alcoholic). KCN attacks through carbon, adding one carbon.

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