Isomerism: structural and E/ZEdexcel A-Level Chemistry: Subtopic test

1. 1
   A chemist is cataloguing the isomers of the alkane C₅H₁₂ and of the haloalkane C₄H₉Br.

   (a)

   How many structural isomers have the molecular formula C₄H₉Br?

   [1 mark]

   • A3
   • B4
   • C5
   • D6

   (b)

   Butan-1-ol and butan-2-ol are isomers. What type of isomerism do they show?

   [1 mark]

   • APosition isomerism
   • BChain isomerism
   • CFunctional group isomerism
   • DE/Z isomerism

   (c)

   Give the IUPAC names of the two branched isomers of C₅H₁₂.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student is studying alkenes with the molecular formulae C₄H₈ and C₅H₁₀, and how the arrangement of groups around the carbon-carbon double bond affects their properties.

   (a)

   Which of these alkenes shows E/Z isomerism?

   [1 mark]

   • ABut-1-ene
   • BPropene
   • C2-methylpropene
   • DBut-2-ene

   (b)

   In one isomer of pent-2-ene, the CH₃ group on carbon 2 and the CH₂CH₃ group on carbon 3 lie on opposite sides of the C=C bond. What is the full name of this isomer?

   [1 mark]

   • A(Z)-pent-2-ene
   • B(Z)-pent-1-ene
   • C(E)-pent-2-ene
   • D(E)-pent-1-ene

   (c)

   Explain what causes E/Z isomerism and state the condition on the groups attached to the C=C bond for a molecule to show it.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Alkenes with the molecular formula C₅H₁₀ are used as models to study isomerism. Ignore cyclic compounds in this question.

   (a)

   Give the structural formula and name of each unbranched alkene with molecular formula C₅H₁₀. State which one shows E/Z isomerism, with a reason.

   [3 marks]

   (b)

   There are three branched alkene isomers of C₅H₁₀. Name them and explain why none of them shows E/Z isomerism.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Several different compounds share the molecular formula C₄H₈: the alkenes but-1-ene, but-2-ene and 2-methylpropene, and the cycloalkane cyclobutane.

   (a)

   Explain, using these compounds as examples, what is meant by structural isomers and describe three types of structural isomerism.

   [6 marks]

   (b)

   Explain why but-2-ene shows E/Z isomerism but but-1-ene and 2-methylpropene do not, and explain how the E and Z isomers are distinguished. State the total number of alkene isomers of C₄H₈, counting stereoisomers.

   [6 marks]

   Total for question 4: 12 marks

End of questions