Halogenoalkanes and nucleophilic substitutionEdexcel A-Level Chemistry: Mind map

Exam questions on Halogenoalkanes and nucleophilic substitution

1. A student has four halogenoalkanes labelled W to Z: 1-bromobutane (W), 2-bromobutane (X), 2-bromo-2-methylpropane (Y) and 1-iodobutane (Z). She plans to warm each with aqueous silver nitrate in ethanol and observe what happens.
   Explain, with reference to the role of water, why a precipitate forms when a halogenoalkane is warmed with aqueous silver nitrate in ethanol.2 marks
2. A chemist wants to lengthen the carbon chain of bromoethane by one carbon atom. She heats bromoethane under reflux with ethanolic potassium cyanide, KCN, and obtains a nitrile.
   Describe, in words, the movement of electrons when the cyanide ion reacts with bromoethane in this nucleophilic substitution.2 marks
3. 2-Bromopropane is warmed separately with aqueous potassium hydroxide and with ethanolic potassium hydroxide, giving different organic products. In a separate experiment, bromoethane is heated with a large excess of ammonia dissolved in ethanol, in a sealed tube.
   Name the organic product formed with each potassium hydroxide solution and state the role of the hydroxide ion in each reaction.3 marks