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Aldehydes and Ketones

Reaction with hydrogen cyanide and the nucleophilic addition mechanism

  • 3 things to know
  • Unit A2 1

Overview

Mechanism by which hydrogen cyanide reacts with a carbonyl compound, product formed when methanal reacts with hydrogen cyanide and role of the potassium cyanide added to the reaction mixture.

What you need to know

Answer each one before you reveal it.

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Process

What is formed when a carbonyl compound meets hydrogen cyanide, by what mechanism, and what comes from ethanal and from propanone?

Key term

Name the type of compound formed when an aldehyde or a ketone reacts with hydrogen cyanide.

Process

Name the mechanism by which hydrogen cyanide reacts with a carbonyl compound.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Name the type of compound formed when an aldehyde or a ketone reacts with hydrogen cyanide.

    Model answer

    A hydroxynitrile is formed, which contains both a hydroxyl group and a nitrile group on the same carbon skeleton.

  2. 2

    Name the mechanism by which hydrogen cyanide reacts with a carbonyl compound.

    Model answer

    The mechanism is nucleophilic addition.

  3. 3

    Write the equation for the reaction of ethanal with hydrogen cyanide and name the product.

    Model answer

    The equation is CH₃CHO + HCN → CH₃CH(OH)CN, and the product is 2-hydroxypropanenitrile.

  4. 4

    Write the equation for the reaction of propanone with hydrogen cyanide and name the product.

    Model answer

    The equation is CH₃COCH₃ + HCN → (CH₃)₂C(OH)CN, and the product is 2-hydroxy-2-methylpropanenitrile.

  5. 5

    Name the product formed when methanal reacts with hydrogen cyanide.

    Model answer

    The product is hydroxyethanenitrile, HOCH₂CN.

  6. 6

    State the conditions used for the reaction of a carbonyl compound with hydrogen cyanide.

    Model answer

    Hydrogen cyanide is used with a trace of potassium cyanide under slightly alkaline conditions at about room temperature.

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