Halogenoalkanes and nucleophilic substitutionEdexcel International A Level Chemistry: Subtopic test

1. 1
   A chemist is using the halogenoalkane CH₃CH₂CHBrCH₃ as the starting material in a multi-step synthesis in a research laboratory.

   (a)

   What is the name of CH₃CH₂CHBrCH₃?

   [1 mark]

   • A1-bromobutane
   • B2-bromobutane
   • C3-bromobutane
   • D2-bromo-3-methylpropane

   (b)

   How is this halogenoalkane classified?

   [1 mark]

   • APrimary
   • BTertiary
   • CSecondary
   • DQuaternary

   (c)

   Explain why the carbon atom in the C–Br bond of a halogenoalkane is attacked by nucleophiles.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In a teaching laboratory, 1-bromopropane is warmed with aqueous potassium hydroxide in a flask fitted with a condenser, and the mixture is heated for about 30 minutes.

   (a)

   What is the organic product of this reaction?

   [1 mark]

   • APropene
   • BPropanal
   • CPropan-2-ol
   • DPropan-1-ol

   (b)

   What is the role of the hydroxide ion in this reaction?

   [1 mark]

   • ANucleophile
   • BElectrophile
   • CFree radical
   • DOxidising agent

   (c)

   Explain why the mixture is heated under reflux rather than simply warmed in an open flask.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student has a sample of 1-bromobutane and plans to convert it into two different organic products using two different reagents.

   (a)

   The first reaction uses potassium cyanide. State the reagent and solvent, name the organic product, and explain why this reaction is useful in synthesis.

   [3 marks]

   (b)

   The second reaction uses a large excess of ammonia dissolved in ethanol, heated in a sealed tube under pressure. Name the organic product and the type of reaction, and explain why a large excess of ammonia is used.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A research student has a sample of 1-bromopropane and carries out several reactions on it to make different products and to identify the halogen it contains.

   (a)

   Describe how aqueous silver nitrate in ethanol can be used to show that the compound contains bromine, and explain, in terms of the mechanism, how the precipitate forms.

   [6 marks]

   (b)

   Describe the mechanism for the reaction of 1-bromopropane with aqueous potassium hydroxide, referring to the movement of electrons, and explain how the mechanism with ammonia differs.

   [6 marks]

   Total for question 4: 12 marks

End of questions