A LevelChemistryCIEExam Questions21. Organic Synthesis21.1 Organic Synthesis

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First exams 2025

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Organic Synthesis (CIE A Level Chemistry)

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21.1 Organic Synthesis

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21.1 Organic Synthesis

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11 mark

Lactic acid occurs naturally, for example in sour milk.

3-9-cie-ial-chemistry-diagram-q1easy

What is a property of lactic acid?

  • It decolourises aqueous bromine rapidly.

  • It is insoluble in water.

  • It reduces Fehling’s reagent.

  • It reacts with sodium carbonate.

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21 mark

Which reagent can be used to convert CH3CH2CO2CH3 into CH3CH2CO2CH2Cl?

  • Chlorine in bright sunlight at 100 °C

  • Concentrated hydrochloric acid at 100 °C

  • Phosphorus pentachloride at room temperature

  • Sulphur dichloride oxide (thionyl chloride, SOCl2) at 50 °C

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31 mark

Which reactions produce a coloured organic compound?

 

1

Ethene   +  cold dilute acidified potassium manganate (VII)

 

2

Ethanol  +  acidified potassium dichromate (VI)

 

3

Ethanal  +  2,4-dinitrophenylhydrazine reagent 

  • 1 only

  • 1 and 2

  • 3 only

  • 2 and 3

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41 mark

A compound C has the following properties:

  • liquid at room temperature
  • soluble in water
  • reacts with aqueous sodium hydroxide

What could C be?

  • Propene

  • Propanol

  • Propanoic acid

  • Propyl propanoate

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51 mark

Tartaric acid can occur naturally, for example in wine, and may be synthesised in the laboratory.

The laboratory synthesis occurs in 2 steps:

     OHCCHO  rightwards arrow with step space 1 on top  intermediate  rightwards arrow with step space 2 on top  HO2CCH(OH)CH(OH)CO2H

                                                                                     tartaric acid

Which reagents could be used for this synthesis?

 

Step 1

Step 2

A

B

C

D

HCl (aq)

H2SO4 (aq)

KCN (aq/alcoholic)

HCN, NaCN (aq/alcoholic)

HCN (g)

K2Cr2O7 / H2SO4 (aq)

K2Cr2O7 / H2SO4 (aq)

H2SO4 (aq)

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    61 mark

    This molecule is responsible for the flavour of spearmint chewing gum.

    3-9-cie-ial-chemistry-diagram-q10easy

    What is a true statement about the functional groups 1 or 2?

    • 1 will undergo nucleophilic addition

    • 1 will undergo electrophilic substitution

    • 2 will undergo nucleophilic addition

    • 2 will undergo electrophilic substitution

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    11 mark

    Sorbic acid is a natural organic compound which is used as a food preservative because it kills fungi. Sorbic acid reacts with bromine in an organic solvent and hydrogen in the presence of a nickel catalyst.

    3-9-cie-ial-chemistry-diagram-q1medium

    How many moles of bromine (in an organic solvent) and of hydrogen (in the presence of a Pt / Ni catalyst) will be incorporated into one mole of sorbic acid by these reactions?

     

    Moles of bromine

    Moles of hydrogen

    A

    B

    C

    D

    2

    2

    2 1 half

    2 size 16px 1 over size 16px 2

    2

    3

    2

    3

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      21 mark

      The naturally-occurring molecule civetone was one of the first know ingredients used in perfumery.

      3-9-cie-ial-chemistry-diagram-q2medium

      Which reagent will not react with civetone?

      • Fehling’s reagent

      • Hydrogen bromide

      • 2,4-dinitrophenylhydrazine reagent

      • Sodium tetrahydridoborate (III), NaBH4

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      31 mark

      An alkene is reacted with acidified manganate (VII) ions, MnO4- . The organic product has a relative molecular mass greater than that of the alkene by 34.

      What are the specific conditions for this reaction?

      • Cold, dilute MnO4-

      • Cold, concentrated MnO4-

      • Hot, dilute MnO4-

      • Hot, concentrated MnO4-

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      41 mark

      Pentanoic acid can be produced from 1-bromobutane using reagents Y and Z as shown below.     

      1-bromobutane  rightwards arrow with reagent space straight Y on top  compound X  rightwards arrow with reagent space straight Z on top  pentanoic acid 

      What could be reagents Y and Z?

       

      Y

      Z

      A

      B

      C

      D

      NaOH (aq) 

      NH3 in ethanol

      KCN in ethanol

      KCN in ethanol

      HCl (aq)

      H+ /Cr2O72- (aq)

      HCl (aq)

      NaOH (aq)

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        51 mark

        In which reaction has a carbocation intermediate?

        • CH3CH2Br + NaOH rightwards arrow CH3CH2OH + NaBr

        • CH2=CH2 + Br2 rightwards arrow CH2BrCH2Br

        • CH3CH3 + Cl2 rightwards arrow CH3CH2Cl + HCl

        • CH3CHO + HCN rightwards arrow with CN to the power of minus on top CH3CH(OH)CN

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        61 mark

        Hept-4-enal naturally occurs in cow’s milk.

        CH3CH2CH=CHCH2CH2CHO

            hept-4-enal

        What organic product is formed when hept-4-enal is reduced with either hydrogen with a nickel catalyst or sodium borohydride?

        • CH3(CH2)5CH3 when hept-4-enal is reduced by H2 / Ni

        • CH3(CH2)5CHO when hept-4-enal is reduced by NaBH4

        • CH3CH2(CH)2(CH2)3OH when hept-4-enal is reduced by H2 / Ni

        • CH3CH2(CH)2(CH2)3OH when hept-4-enal is reduced by NaBH4

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        11 mark

        The diagram shows the structure of the naturally-occurring molecule cholesterol.

        3-9-cie-ial-chemistry-diagram-q1hard

        Two separate test tubes of cholesterol are used in an experiment. One test tube of cholesterol is treated with cold, dilute acidified KMnO4, and the other is treated with hot, concentrated acidified KMnO4.

        Which row correctly describes the change in the number of chiral carbon atoms in the molecule during each reaction and the structure of the product in each test tube?

         

        Cold, dilute acidified KMnO4

        Hot, concentrated acidified KMnO4
         

        Change in the number of chiral carbons

        Number of hydroxy groups in product

        Change in the number of chiral carbons

        Number of 6-membered rings remaining in product

        A

        B

        C

        D

        +1

        +1

        +2

        +2

        1

        1

        3

        3

        0

        -1

        -1

        0

        2

        3

        2

        3

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          21 mark

          The cyclic compound G is heated with dilute hydrochloric acid.

          3-9-h-2

          What are the products of the reaction?

          • HOCH2CO2H and H2NCH2CO2H

          • H2NCOCH2OH and HOCH2CHO

          • HOCH2CONH3+ and HOCH2CHO

          • HO2CCH2NH3+ and HO2CCH2OH

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          31 mark

          Santonin is a drug that has been used to treat a worm infection.

          3-9-cie-ial-chemistry-diagram-q5hard

          When santonin is first treated with warm dilute H2SO4, product X is formed. If X is treated with cold acidified KMnO4, the final product Y is obtained.

          How many atoms of hydrogen in each molecule of product Y could be displaced in a reaction with sodium metal?

          • 2

          • 4

          • 5

          • 6

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          41 mark

          Compound M is used in leather processing.

          3-9-cie-ial-chemistry-diagram-q6hard

          Compound M is synthesised in the presence of concentrated sulfuric acid and heat.

          Which other starting material(s) are required to synthesise compound M?

          • CH3COOH only

          • HOCH2COOH only

          • CH3COOCH2COOH only

          • CH3COOH mixed with HOCH2COOH

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          51 mark

          Mixture F is produced upon refluxing compound G with aqueous sodium hydroxide. 

          Upon distillation with acidified potassium dichromate (VI) propanone is produced. Mixing J with aqueous silver nitrate and dilute nitric acid gives a cream precipitate.

          What could compound G be?

          • CH3CHICH3

          • CH3CHBrCH3

          • CH3CH2CH2I

          • CH3CH2CH2Br

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          61 mark

          Antipyrine is a drug used to reduce fever. The initial step of its synthesis is the reaction of phenylhydrazine with compound X.

          3-9-cie-ial-chemistry-diagram-q8hard

          What is the product Y?

          • 3-9-h-8a

          • 3-9-h-8b

          • 3-9-h-8c

          • 3-9-h-8d

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          71 mark

          Ibuprofen is an anti-inflammatory drug, the structure of which is shown below.

          3-9-cie-ial-chemistry-diagram-q9hard

          Which reaction leads to the formation of ibuprofen?

          • 3-9-h-9a

          • 3-9-h-9b

          • 3-9-h-9c

          • 3-9-h-9d

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