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4 marksFunctional Group Analysis, Reactions and Mechanisms

CAPE Chemistry Unit 2 · May/June 2021 · Paper 2 · Question 1(b)(iii)

A gaseous hydrocarbon P (volume 10 cm³, formula CₓHᵧ) was mixed with 70 cm³ of oxygen and exploded. After cooling, the gaseous mixture occupied 55 cm³. After shaking with aqueous sodium hydroxide, the volume reduced to 35 cm³. The remaining gas was oxygen. All volumes were measured at constant pressure. The combustion equation is CₓHᵧ + (x + y/4)O₂ → x CO₂ + y/2 H₂O.

Outline the reaction mechanism for the reaction of P with liquid bromine, using appropriate notations and equations.

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Other parts of this question

  1. 1(a)(i)Define the term 'structural isomerism'.[2 marks]
  2. 1(a)(ii)Identify TWO types of structural isomers, giving an example of EACH.[4 marks]
  3. 1(b)(i)Calculate the molecular formula of the hydrocarbon, P.[3 marks]
  4. 1(b)(ii)Write the displayed structural formula of P.[1 mark]
  5. 1(b)(iv)Identify the type of reaction mechanism outlined in (b)(iii) on page 5.[1 mark]
  6. 1(c)(i)Write the displayed structural formula of TWO isomers of Q.[2 marks]
  7. 1(c)(ii)State whether Compound Q exhibits geometric (cis/trans) isomerism.[1 mark]
  8. 1(c)(iii)State TWO reasons for your answer in (c)(ii).[2 marks]
  9. 1(c)(iv)Outline the mechanism for the reaction between Compound Q and HBr, using curved arrows to show the movement of electrons.[4 marks]
  10. 1(c)(v)State the type of reaction mechanism outlined in (c)(iv).[1 mark]
  11. 1(d)(i)Describe the observations expected for EACH of the following reactions: Aqueous bromine is added to liquid pentane (in sunlight).[2 marks]
  12. 1(d)(ii)Describe the observations expected for EACH of the following reactions: Aqueous bromine is added to liquid pentane (without sunlight).[1 mark]
  13. 1(d)(iii)Describe the observations expected for EACH of the following reactions: Cold acidified potassium permanganate solution is added to liquid pentane.[2 marks]

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