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A-LevelChemistryHydroxy compounds9701/21 · May/June 2021 · Q612 Marks

Propene, C₃H₆, reacts with H₂O in the presence of an acid catalyst to form an alcohol with molecular formula C₃H₈O.

  1. (a)Name this type of reaction.[1]
  2. (b)Name the catalyst used and state the conditions needed for this reaction to occur. catalyst conditions[2]
  3. (c)Complete the table to show the numbers of sigma (σ) bonds and pi (π) bonds present in propene, C₃H₆, and C₃H₈O. C₃H₆ C₃H₈O σ π[2]
  4. (d)(i)The reaction of propene, C₃H₆, with H₂O occurs in a two-step mechanism. In step 1 C₃H₆ reacts with the catalyst, H⁺, to form a carbocation. Draw structures to identify the more stable and less stable carbocations which can form in step 1. Explain your answer. more stable carbocation less stable carbocation explanation[3]
  5. (d)(ii)Name the major organic product formed from the reaction of propene, C₃H₆, with H₂O.[1]
  6. (e)(i)2-bromopropane reacts to form propene, hydrogen bromide and water under certain conditions. Name this type of reaction.[1]
  7. (e)(ii)Describe the reagents and conditions needed to favour this reaction. reagents conditions[2]

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

  1. [1] addition
  2. [1] M1 catalyst = sulfuric acid / phosphoric(V) acid
  3. [1] M2 conditions of reaction = steam / heat (and pressure)
  4. [2] σ π C3H6 8 1 C3H8O 11 0
  5. [1] M1 more stable = CH3C+(H)(CH3)
  6. [1] M2 less stable = CH3CH2C+(H2) /
  7. [1] M3 greater (positive) inductive effect of two alkyl groups OR greater electron donation of two alkyl groups owtte
  8. [1] propan-2-ol
  9. [1] elimination
  10. [1] M1 NaOH/KOH
  11. [1] M2 ethanolic solution / ethanol / alcohol + heat

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About this question

Topic
Hydroxy compounds, A-Level Chemistry (syllabus 9701). Structured question, 12 marks.
Source
A-Level Chemistry, May/June 2021 Paper 2 Variant 1, question 6.

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