A LevelChemistryCIEExam Questions3. Organic Chemistry3.9 Organic Synthesis

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Organic Synthesis (CIE A Level Chemistry)

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3.9 Organic Synthesis

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3.9 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

The characteristic smell of cut grass is due to the compound trans-hex-3-enal. The human nose is very sensitive to this compound and is able to detect 0.25 parts per billion in air.

3-9-cie-ial-chemistry-diagram-q4easy

Which reagents will react with trans-hex-3-enal?

 

1

Fehling’s reagent 

 

2

Sodium borohydride

 

3

Sodium

  • 1 only

  • 1 and 2

  • 2 only

  • 2 and 3

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51 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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61 mark

The following compounds are heated under reflux with an excess of hot acidified potassium dichromate (VI). 

Which gives a product with a chiral centre?

3-9-cie-ial-chemistry-diagram-q6easy

  • 1 only

  • 1 and 2

  • 3 only

  • 2 and 3

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71 mark

Disaccharides, C12H22O11, are important in the human diet as they are a source of fast energy. Lactose and sucrose are both disaccharides which can be hydrolysed to release glucose.

lactose + H2O rightwards arrow CH2OH(CHOH)4CHO + CH2OH(CHOH)4CHO

                        glucose                           galactose

          sucrose + H2O rightwards arrow CH2OH(CHOH)4CHO + CH2OH(CHOH)3COCH2OH

                      glucose                           fructose

Which statements about these hydrolysis products are correct?

 

1

Both products of lactose hydrolysis are ketones.

 

2

Both products of lactose hydrolysis are optical isomers.

 

3

Both products of sucrose hydrolysis have structural isomers.

  • 1 only

  • 1 and 2

  • 2 and 3

  • 1, 2 and 3

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81 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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    91 mark

    DHA is an omega-3 fatty acid which is used to treat heart disease and high cholesterol as well as being essential for brain development during pregnancy.

    3-9-cie-ial-chemistry-diagram-q9easy

    Which observations would be made when testing this substance?

     

    1

    Hydrogen is produced when sodium is added.

     

    2

    A silver precipitate is produced when Tollens’ reagent is added.

     

    3

    A coloured precipitate is produced when 2,4-dinitrophenylhydrazine reagent is added.

    • 1 only

    • 1 and 3

    • 2 and 3

    • 1, 2 and 3

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    101 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

      Investigation of an unknown compound, X, was carried out in a laboratory and the following properties were discovered:

      • X has the molecular formula C9H12O;
      • X is unreactive towards mild oxidising agents.

      What is the structure of the compound formed by dehydration of X?

      3-9-cie-ial-chemistry-diagram-q3medium

      • 3 only

      • 1 and 2

      • 1, 2 and 3

      • 3 and 4

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      41 mark

      A student carried out a series of tests on the compound shown in the diagram below.

      3-9-cie-ial-chemistry-diagram-q4medium

      Which pairs of reagents would both give a positive result for this compound?

       

      1

      Sodium carbonate and 2,4-dinitrophenylhydrazine reagent

       

      2

      Fehling’s reagent and aqueous bromine

       

      3

      Tollens’ reagent and a solution containing acidified dichromate (VI) ions 

      • 1 only

      • 1 and 2

      • 2 and 3

      • 1, 2 and 3

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      51 mark

      1, 2 and 3 give the molecular formula of organic compounds.

      Which would cause decolorisation of aqueous bromine and react with sodium to evolve hydrogen gas?

       

      1

      C3H6O

       

      2

      C3H8O 

       

      3

      C3H4O2

      • 1, 2 and 3

      • 1 and 3

      • 2 and 3

      • 2 only

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      61 mark

      The structure of monosodium glutamate (MSG) is shown below. This molecule is used as a flavour enhancer in foods.

      3-9-cie-ial-chemistry-diagram-q6amedium

      It may be prepared starting from the following compound.

      3-9-cie-ial-chemistry-diagram-q6bmedium

      Which set of reagents and reaction conditions could be used to prepare monosodium glutamate?

       

      1

      Heat under reflux with NaOH (aq) 

       

      2

      Heat with sodium methanoate, HCO2-Na+

       

      3

      Heat under reflux with ethanolic KCN followed by hydrolysis with NaOH (aq)

      • 1, 2 and 3

      • 1 and 2

      • 2 and 3

      • 1 only

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      71 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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      81 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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        91 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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        101 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

          Cholesterol found in the cell membrane of animal cells has the following structure.

          3-9-cie-ial-chemistry-diagram-q3hard

          Which statements are correct?

           

          1

          Cholesterol forms an aldehyde after oxidation by acidified sodium dichromate (VI) to 

           

          2

          Cholesterol reacts with bromine to form a compound which has two new chiral centres

           

          3

          Cholesterol reacts with a mixture of concentrated sulphuric acid and ethanoic acid 

          • 1, 2 and 3

          • 1 and 2

          • 2 and 3

          • 1 only

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          41 mark

          The structure of the naturally-occurring molecule cholesterol is shown below.

          Z0P8V9Gu_3-9-cie-ial-chemistry-diagram-q3hard

          Student 1 says that cholesterol displays cis-trans isomerism at the C = C double bond. 

          Student 2 says all carbon atoms within the rings of cholesterol all lie in the same plane. 

          Which of the students are correct?

          • Both 1 and 2

          • 1 only

          • 2 only

          • Neither 1 nor 2

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          51 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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          61 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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          71 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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          81 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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          91 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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          101 mark

          When the apparatus below was used with compound E, a brick-red precipitate formed in the right-hand tube.

          3-9-cie-ial-chemistry-diagram-q10hard

          Which compound could be E?

           

          1

          CH3OH 

           

          2

          CH3CH2CH2OH

           

          3

          CH3CH(OH)CH3

          • 1, 2 and 3

          • 1 and 2

          • 2 and 3

          • 1 only

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