Organic Chemistry: Carbonyls (Edexcel International A Level Chemistry)

Exam Questions

1a1 mark

The compound menthol has the structure shown.
Some of the carbon atoms are labelled P, Q, R and S.

q8-paper-4-2021-june-edexcel-ial-chemistry

a)
What is the number of chiral centres in a molecule of menthol?

  • 1

  • 2

  • 3

  • 4

1b1 mark
b)
Which of the carbon atoms is responsible for a peak at 72 ppm in the 13C NMR spectrum of menthol?
  • P

  • Q

  • R

  • S

1c1 mark
c)
Four groups of students warmed samples of menthol with sodium dichromate(VI) in acid. They purified the reaction mixture and carried out a series of qualitative tests on the organic product.

The findings of each group in the class are shown in the table.

q8c-paper-4-2021-june-edexcel-ial-chemistry

  Qualitative test
Group

Add

2,4-dinitrophenylhydrazine

Warm with
Fehling’s solution
Add
PCl5
  One
  Two
  Three
  Four

A tick () shows a positive result, a cross () shows a negative result.

Which group recorded the results you would expect?
  • One

  • Two

  • Three

  • Four

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21 mark

How many structural isomers with the molecular formula C5H10O react with Tollens’ reagent?

  • 2

  • 3

  • 4

  • 5

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31 mark

Ethanal and propane have the same molar mass but ethanal has a much higher boiling temperature.

Ethanal is fully miscible in water but propane is almost insoluble.

Which intermolecular forces of ethanal are mainly responsible for the differences in these properties?

      Higher boiling temperature Greater solubility in water
  A hydrogen bonds hydrogen bonds
  B permanent dipole forces permanent dipole forces
  C hydrogen bonds permanent dipole forces
  D permanent dipole forces hydrogen bonds

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    4a1 mark

    Propanone reacts with iodine in both acidic and alkaline conditions.

    a)
    The products of the reactions under the stated conditions include

          Acidic conditions Alkaline conditions
      A CH3I CH3COO
      B CH3COCI3 CH3COO
      C CH3COCH2I CH3I
      D CH3COCH2I CHI3
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      1 mark
      b)

      The rate equation for the reaction between propanone and iodine in acidic conditions is

      rate = k[H+][CH3COCH3]

      The reaction was carried out at two different pH values, all other conditions remaining unchanged.

      In the first reaction pH = 2.0

      In the second reaction the rate was found to be 1/3 of the original value.

      What was the pH of the second reaction, to 1 decimal place?

      • 0.7

      • 1.5

      • 2.5

      • 2.7

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      51 mark

      An unknown aldehyde may be identified by measuring the melting temperature of the purified precipitate formed in its reaction with

      • 2,4-dinitrophenylhydrazine

      • Fehling’s solution

      • potassium dichromate and sulfuric acid

      • Tollens’ reagent

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      61 mark

      A compound X, with molecular formula C5H10O , gave an orange precipitate with 2,4-dinitrophenylhydrazine.

      X gave a silver mirror with Tollens’ reagent.

      Which of these could not be X?

      q13-paper-4-jan-2021-edexcel-ial-chemistry

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