Numford
Organic conversion

Propanone to propene

2 steps: reduction, then elimination

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

  1. O
    PropanoneCH₃COCH₃Ketone
  2. Step 1

    NaBH₄

    i

    Hydride reduction of a ketone gives the secondary alcohol.

    Also written: LiAlH₄, then H₃O⁺

    OH
    Propan-2-olCH₃CH(OH)CH₃Alcohol
  3. Step 2

    85% H₃PO₄

    440 K

    i

    Secondary alcohols dehydrate more easily than primary ones.

    PropeneCH₃CH=CH₂Alkene

Exam answer

  1. Step 1: Propanone to propan-2-ol: NaBH₄.
  2. Step 2: Propan-2-ol to propene: 85% H₃PO₄, 440 K.
Alternative routes (1)
  • Propanone → Propan-2-ol → 2-Bromopropane → Propene
    1. Propanone to propan-2-ol: NaBH₄.
    2. Propan-2-ol to 2-bromopropane: red P + Br₂ (PBr₃).
    3. 2-Bromopropane to propene: alc. KOH, heat.
Why these reagents

Reagent and reason, step by step

  • Step 1: Propanone to propan-2-ol: NaBH₄ Hydride reduction of a ketone gives the secondary alcohol.
  • Step 2: Propan-2-ol to propene: 85% H₃PO₄, 440 K Secondary alcohols dehydrate more easily than primary ones.
Questions

Propanone to propene: quick answers

How many steps does it take to convert propanone to propene?

2 steps: Propanone, then propan-2-ol, then propene.

Which named reaction is used to convert propanone to propene?

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

What is the reagent for step 1 of propanone to propene?

Propanone to propan-2-ol: NaBH₄. Hydride reduction of a ketone gives the secondary alcohol.

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