Reaction types, mechanisms, nucleophiles and electrophilesEdexcel International A Level Chemistry: Mind map

Exam questions on Reaction types, mechanisms, nucleophiles and electrophiles

1. A student summarises five reactions of ethene and related compounds. Reaction 1: ethene reacts with hydrogen bromide to form bromoethane. Reaction 2: bromoethane is warmed with aqueous sodium hydroxide to form ethanol and sodium bromide. Reaction 3: bromoethane is warmed with ethanolic sodium hydroxide to form ethene, sodium bromide and water. Reaction 4: ethanol is warmed with acidified potassium dichromate(VI) to form ethanal. Reaction 5: many ethene molecules join under high pressure to form poly(ethene).
   Name the type of reaction in Reaction 3 and in Reaction 5, and state what happens to the organic molecules in each.2 marks
2. Bromoethane reacts with aqueous hydroxide ions to form ethanol: CH₃CH₂Br + OH⁻ → CH₃CH₂OH + Br⁻. The reaction can be explained by a mechanism in which curly arrows show the movement of pairs of electrons.
   Describe, in terms of the movement of electron pairs, how bromoethane forms ethanol in this reaction.2 marks
3. Ethene reacts with bromine at room temperature to form 1,2-dibromoethane: CH₂=CH₂ + Br₂ → CH₂BrCH₂Br. The reaction occurs readily even though ethene and bromine are both non-polar molecules.
   Explain why ethene is attacked by electrophiles, and why bromine behaves as an electrophile in this reaction.3 marks