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CAIE A-Level Chemistry 17.1 Aldehydes & ketones Question Bank

Practise aldehyde and ketone questions using preparation routes, nucleophilic addition mechanisms and tests for carbonyl identity.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • interpret oxidation and reduction sequences to identify aldehyde, ketone or alcohol products
  • draw or describe HCN addition mechanisms using CN- attack and protonation
  • use 2,4-DNPH, Tollens' reagent and alkaline I2 to identify unknown carbonyls

Covered syllabus points

17.1.1—Preparation of aldehydes and ketones17.1.2—Describe17.1.3—Reactions of hydrogen cyanide17.1.4—2,4-DNPH carbonyl test17.1.5—The nature (aldehyde or ketone) of an unknown17.1.6—Iodoform test for CH3CO- group

17.1 Aldehydes and ketones question 1

[Maximum number: 8]

4(CH3)3CCHO4\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCHO} is used in the synthesis of some antibiotics.

Question (a)

(a)

Two reaction sequences are shown.

Figure for Question (a) — CAIE A-Level Chemistry AS
Figure for Question (a) — CAIE A-Level Chemistry AS
[ 2 ]

Question (i)

(i)

Reaction 1 is an oxidation reaction.

Identify the reagent(s) and conditions for reaction 1.

[ 1 ]

Question (ii)

(ii)

Give the balanced equation for the reaction of (CH3)3CCHO\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCHO} with NaBH4\mathrm{NaBH}_{4} to form S.

Use [H] to represent an atom of hydrogen provided by NaBH4\mathrm{NaBH}_{4}.

[ 1 ]

Question (b)

(b)

X, Y and Z are all isomers of (CH3)3CCHO\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCHO}.

A summary of some of the reactions and properties of X, Y and Z is shown in the table.

Table for Question (b) — CAIE A-Level Chemistry AS
[ 6 ]

Question (i)

(i)

X and Y each contains a carbonyl group.

Complete the table with the expected observations for the reactions of X and Y with 2,4-DNPH.

[ 1 ]

Question (ii)

(ii)

Identify the functional group present in Y that causes the recorded observation with Fehling's solution.

[ 1 ]

Question (iii)

(iii)

X contains a carbonyl group. X reacts with HCN , in the presence of a small amount of NaCN , to form (C2H5)2C(OH)CN\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{C}(\mathrm{OH}) \mathrm{CN} as shown.

X+HCN→(C2H5)2C(OH)CN\mathbf{X}+\mathrm{HCN} \rightarrow\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{C}(\mathrm{OH}) \mathrm{CN}

Draw the mechanism of the reaction of X with HCN .
- Draw the structure of X and the intermediate.
- Include all charges, partial charges, lone pairs and curly arrows.

Figure for Question (iii) — CAIE A-Level Chemistry AS
[ 3 ]

Question (iv)

(iv)

State the role of NaCN in the reaction in (c)(vii).

[ 1 ]
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