Mr Cole Chemistry

Hydrolysis of Nitriles

These questions are not relevant to AQA A-level Chemistry but are important for OCR A-level students.

  • Questions
  • Answers
  1. Ethanenitrile will react in an acid hydrolysis reaction.
    1. Draw the skeletal formula of ethanenitrile.
    2. Write the equation for the reaction between hydrochloric acid and ethanenitrile.
    3. The first two steps of the mechanism are outlined below but are missing lone pairs and curly arrows.
      • Fill in the lone pairs and curly arrows.
      • State how the nitrogen is behaving in the first step.
      • State how the water is behaving in the second step.
  2. Nitriles can also undergo hydrolysis reacts in alkaline conditions.
    1. Write an equation for the reaction of propanenitrile and sodium hydroxide.
    2. The OH– ion acts as a nucleophile in the first step of the reaction. Suggest which atom in propanenitrile is most likely to be attacked by a nucleophile. Explain your answer.
  3. The following reactants are reacted. Identify the products of the reactions and write the equation for the reactions.
    1. 2-chloroethanenitrile and aqueous sodium hydroxide.
    2. Propenenitrile and concentrated sulfuric acid.
    3. Aminoethanenitrile and hydrochloric acid.
  1. Ethanenitrile will react in an acid hydrolysis reaction.
    1. Draw the skeletal formula of ethanenitrile.
    2. Write the equation for the reaction between hydrochloric acid and ethanenitrile.
      CH3CN + 2H2O + HCl –> CH3COOH + NH4Cl
    3. The first two steps of the mechanism are outlined below but are missing lone pairs and curly arrows.
      • Fill in the lone pairs and curly arrows.
      • State how the nitrogen is behaving in the first step.
        A base – it is accepting a hydrogen ion / donating a pair of electrons.
      • State how the water is behaving in the second step.
        A nucleophile – it donates a pair of electrons to a positive centre.
  2. Nitriles can also undergo hydrolysis reacts in alkaline conditions.
    1. Write an equation for the reaction of propanenitrile and sodium hydroxide.
      CH3CH2CN + NaOH + H2O –> CH3CH2COO-Na+ + NH3
    2. The OH– ion acts as a nucleophile in the first step of the reaction. Suggest which atom in propanenitrile is most likely to be attacked by a nucleophile. Explain your answer.
      The Carbon bonded to the nitrogen. The carbon is partially positive due to the triple bonds with the nitrogen, which is more electronegative. This makes it vulnerable to attack by the lone pair of electrons on the oxygen of the hydroxide.
  3. The following reactants are reacted. Identify the products of the reactions and write the equation for the reactions.
    1. 2-chloroethanenitrile and aqueous sodium hydroxide.
      CH2ClCN + 2NaOH + H2O –> CH2OHCOO–Na+ + NH3 + NaCl
    2. Propenenitrile and concentrated sulfuric acid.
      CH2CHCN + ½H2SO4 + 3H2O –> CH3CH(OH)COOH + ½(NH4)2SO4
    3. Aminoethanenitrile and hydrochloric acid.
      NH2CH2CN + 2HCl + 2H2O –> HOOCCH2NH3+Cl– + NH4Cl
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