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Aldehydes and Ketones

Nucleophilic addition of HCN to aldehydes and ketones

  • 3 things to know
  • Component 2

Overview

Recall questions on the product and its name, the mechanism named and described with each curly arrow, the attacking species and where it attacks, why a racemic mixture results, why the product from methanal or propanone is not chiral, and the hazards of the reagent.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Describe the second step of the addition of HCN, saying what each curly arrow moves.

Key term

Explain why the addition of HCN to a carbonyl compound proceeds fastest at a pH of about 9 to 10

Key term

At what temperature is the addition of hydrogen cyanide to a carbonyl compound carried out?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    How is the hydrogen cyanide for this reaction usually supplied in the laboratory?

    Model answer

    It is generated in the flask by adding dilute sulfuric acid to potassium cyanide or sodium cyanide, so the highly toxic gas is never handled as such.

  2. 2

    At what temperature is the addition of hydrogen cyanide to a carbonyl compound carried out?

    Model answer

    The mixture is held at about 10 to 20 °C.

  3. 3

    Name the nucleophile that attacks the carbonyl compound in this reaction.

    Model answer

    The cyanide ion, CN⁻.

  4. 4

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

    Model answer

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

  5. 5

    Name and give the formula of the product formed when propanone reacts with hydrogen cyanide.

    Model answer

    2-hydroxy-2-methylpropanenitrile, (CH₃)₂C(OH)CN.

  6. 6

    Name the mechanism of this reaction and state where the attack takes place.

    Model answer

    It is nucleophilic addition, and the attack takes place at the δ+ carbon atom of the carbonyl group.

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An is formed.
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