Chlorination of alkanesAQA A-Level Chemistry: Mind map

Exam questions on Chlorination of alkanes

1. Methane reacts with chlorine in the presence of ultraviolet light to form chloromethane, CH₃Cl, and hydrogen chloride. The reaction takes place by a free-radical substitution mechanism.
   Explain why ultraviolet light is needed for the initiation step.2 marks
2. When methane reacts with chlorine in ultraviolet light, the product mixture also contains small amounts of ethane, C₂H₆, and dichloromethane, CH₂Cl₂.
   Write equations for the two propagation steps that convert chloromethane, CH₃Cl, into dichloromethane, CH₂Cl₂.2 marks
3. Ethane, CH₃CH₃, reacts with chlorine in the presence of ultraviolet light to form chloroethane, CH₃CH₂Cl, by the same type of mechanism as the reaction of methane with chlorine.
   Write equations for the initiation step and the two propagation steps in this reaction.3 marks