ASChemistryCIEExam Questions17. Carbonyl Compounds17.1 Aldehydes & Ketones

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Aldehydes & Ketones (CIE AS Chemistry)

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17.1 Aldehydes & Ketones

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17.1 Aldehydes & Ketones

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11 mark

What is formed when butanone is refluxed with a solution of NaBH4?

  • Butane

  • Butan-1-ol

  • Butan-2-ol

  • Butanal

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21 mark

In 1903 Arthur Lapworth became the first chemist to investigate a reaction mechanism. The reaction of hydrogen cyanide with propanone.

What do we now call the mechanism of this reaction?

  • Nucleophilic substitution

  • Nucleophilic addition

  • Electrophilic substitution

  • Electrophilic addition

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31 mark

Which carbonyl compound(s) react with both LiAlH4 and Tollens’ reagent?

  • Ketones only

  • Aldehydes only

  • Both aldehydes and ketones

  • Neither aldehydes nor ketones

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41 mark

In a nucleophilic addition reaction, aqueous methanolic solution of NaBH4 acts as a reducing agent when added to propanal, CH3CH2CHO.

What is the first step of this mechanism?

  • Attack of an H– ion at the oxygen atom of the carbonyl group.

  • Attack of an H+ ion at the oxygen atom of the carbonyl group.

  • Attack of an H– ion at the carbon atom of the carbonyl group.

  • Attack of an H+ ion at the carbon atom of the carbonyl group.

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51 mark

The characteristic smell of burnt sugar is partly caused by the following compound.

3-5-e-5

There are two functional groups in the compound. 

Which reagent will react with both functional groups?

  • Sodium hydroxide

  • Hydrogen cyanide

  • Fehling’s solution

  • Acidified potassium dichromate (VI)

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61 mark

In which reaction is the organic compound oxidised?

  • CH3CH2CN + dilute H2SO4

  • CH3CH2CHO + Tollens’ reagent

  • CH3COCH2CH3 + 2,4-dinitrophenylhydrazine reagent

  • CH3CH2CH2OH + concentrated H3PO4

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71 mark

Ethanal, CH3CHO, is reduced using NaBH4 in aqueous ethanol in a nucleophilic addition reaction.

What is the first step of this mechanism?

  • The oxygen atom of the carbonyl group is attacked by an H– ion

  • The oxygen atom of the carbonyl group is attacked by an H+ ion

  • The carbon atom of the carbonyl group is attacked by an H– ion

  • The carbon atom of the carbonyl group is attacked by an H+ ion

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81 mark

The orange colour of carrots is due to the presence of β-carotene, the structure of which is shown in the diagram below.

3-5-cie-ial-chemistry-diagram-q9easy

Hot, concentrated, acidified KMnO4 will oxidise β-carotene.

When an individual molecule of β-carotene is oxidised in this way there are multiple possible products.

How many of these product molecules contain a ketone functional group?

  • 3

  • 6

  • 9

  • 12

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91 mark

Hex-3-enal is used as a flavouring agent.

CH3CH2CH=CHCH2CHO

    hex-3-enal

Which row correctly shows the product formed when hex-3-enal is treated with the given reducing agent?

 

Product

Reducing agent

A

B

C

D

CH3(CH2)4CH3

CH3(CH2)4CH2OH

CH3(CH2)4CHO

CH3(CH2)4CHO

H2 + Ni

NaBH4

H2 + Ni

NaBH4

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    11 mark

    When alkaline I2 solution is added to butanone, a yellow precipitate is formed. 

    Which of the following compounds is responsible for the precipitate?

    • CH3CH2COCH2I

    • CH3CH2CO2-

    • CH3CHICOCH3

    • CHI3

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    21 mark

    The colour of warm acidified sodium dichromate (VI) changes from orange to green when added to compound Y. 1 mol of Y reacts with 2 mol of hydrogen cyanide in the presence of potassium cyanide.

    What could Y be?

    • H2C=CHCH2CHO

    • CH3CH2CH2CHO

    • OHCCH2CH2CHO

    • CH3COCH2COCH3

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    31 mark

    Hydroxyethanal has the structural formula HOCH2CHO. 

    In an experiment hydroxyethanal is heated under reflux with an excess of acidified potassium dichromate (VI) until no further oxidation takes place.

    What is the skeletal formula of the organic product formed in the experiment?

    • 3-5-m-5a

    • 3-5-m-5b

    • 3-5-m-5c

    • 3-5-m-5d

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    41 mark

    Which reagent will give similar results with both propanone and propanal?

    • 2,4-dinitrophenylhydrazine reagent

    • Acidified aqueous potassium dichromate (VI)

    • An aqueous solution containing [Ag(NH3)2]+ (Tollens’ reagent)

    • An alkaline solution containing complexed Cu2+ ions (Fehling’s solution)

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    51 mark

    Carvone is used as a flavouring for spearmint chewing gum.

    3-5-cie-ial-chemistry-diagram-q7medium

    When carvone is heated for a prolonged time with hot concentrated acidified potassium manganate (VII) the products carbon dioxide and compound X are formed.

    X contains nine carbon atoms and reacts with 2,4-dinitrophenylhydrazine reagent.

    What is the maximum number of molecules of 2,4-dinitrophenylhydrazine that will react with one molecule of X?

    • 4

    • 3

    • 2

    • 1

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    61 mark

    When compounds 1, 2 and 3 react with PCl5, hydrogen chloride is evolved. However, only one of the three reacts with 2,4-dinitrophenylhydrazine reagent.

    Which one of the following combinations could be 1, 2 and 3?

    3-5-m-10

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      11 mark

      When HCN reacts with butanal, CH3CH2CH2CHO, product X is formed. If X is then hydrolysed by aqueous acid, product Y is produced.

      When pentanal, C4H9CHO, is heated under reflux with acidified potassium dichromate (VI), product Z is formed.

      What is the difference in relative molecular mass of products Y and Z?

      • 12

      • 14

      • 16

      • 18

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      21 mark

      Cyanohydrins (also called hydroxynitriles) can be made from carbonyl compounds by generating CN– ions from HCN in the presence of a weak base.

      3-5-cie-ial-chemistry-diagram-q2hard

      In a similar reaction, –CH2CO2CH3 ions are generated from CH3CO2CH3 by strong bases.

      Which compound can be made from an aldehyde and CH3CO2CH3 in the presence of a strong base?

      • CH3CH(OH)CO2CH3

      • CH3CO2CH2CH(OH)CH3

      • CH3CH2CH(OH)CH2CO2CH3

      • (CH3)2C(OH)CH2CO2CH3

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      31 mark

      When compound T reacts with its own oxidation product, a sweet-smelling liquid is produced. 

      What is the identity of compound T? 

      • Butanal

      • Butanone

      • Butan–1–ol

      • Butanoic acid

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      41 mark

      Three separate test tubes, 1, 2 and 3, each contain 1 mol of compound X. 

      An excess of sodium borohydride is added to test tube 1 and an excess of acidified sodium permanganate is added to test tube 2. No reagent is added to test tube 3.  

      Following this, 2 mol of HCN (g) is added to each test tube and the HCN completely reacts in all 3.

      What could X be?

      • CH3COCH2CH2CHO

      • CH3CH(OH)COCH3

      • H2C=CHCH2CHO

      • HOCH3CH2CH2CHO

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