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CAIE A-Level Chemistry AS 17.1 Aldehydes and Ketones Questions

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

Question 1

[Maximum number: 2]

Compound X contains the same functional groups as citric acid.

citric acid

citric acid

The table describes some of the similarities and differences between citric acid and compound X.

Table for Question 1 — CAIE A-Level Chemistry AS

Explain why compound X reacts with acidified Cr2O72−\mathrm{Cr}_{2} \mathrm{O}_{7}{ }^{2-} but citric acid does not.

Question 2

[Maximum number: 1]

Which statement about butanone is correct?

A

Butanone can be dehydrated by concentrated sulfuric acid to give CH2=CHCH=CH2\mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CH}_{2}.

B

Butanone gives a positive result with Tollens' reagent.

C

Butanone reacts with HCN by an electrophilic addition mechanism.

D

Butanone reacts with NaBH4\mathrm{NaBH}_{4} to give a chiral product.

Question 3

[Maximum number: 1]

The mechanism for the reaction between ethanal and hydrogen cyanide starts with the step shown.

Figure for Question 3 — CAIE A-Level Chemistry AS

What is the correct structure of the intermediate ion formed, and what is the next step in this mechanism?

A
Figure for Question 3 — CAIE A-Level Chemistry AS — Option A
B
Figure for Question 3 — CAIE A-Level Chemistry AS — Option B
C
Figure for Question 3 — CAIE A-Level Chemistry AS — Option C
D
Figure for Question 3 — CAIE A-Level Chemistry AS — Option D

Question 4

[Maximum number: 1]

Which compound will produce a yellow-orange precipitate when added to 2,4-dinitrophenylhydrazine?

A
Figure for Question 4 — CAIE A-Level Chemistry AS — Option A
B
Figure for Question 4 — CAIE A-Level Chemistry AS — Option B
C
Figure for Question 4 — CAIE A-Level Chemistry AS — Option C
D
Figure for Question 4 — CAIE A-Level Chemistry AS — Option D

Question 5

[Maximum number: 1]

Compound Y:

- changes the colour of acidified K2Cr2O7\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} from orange to green

- has no effect on Fehling's reagent

- produces an orange precipitate with 2,4-dinitrophenylhydrazine reagent.

What is compound Y ?

A
Figure for Question 5 — CAIE A-Level Chemistry AS — Option A
B
Figure for Question 5 — CAIE A-Level Chemistry AS — Option B
C
Figure for Question 5 — CAIE A-Level Chemistry AS — Option C
D

HOCH2CH2CH2CH2OH\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}

Question 6

[Maximum number: 1]

X is a non-cyclic ketone with a single carbonyl group and no other functional groups. Ketone X has the following properties.
- When ketone X is treated with NaBH4\mathrm{NaBH}_{4}, the organic product has a Mr2.3256%M_{\mathrm{r}} 2.3256 \% greater than the MrM_{r} of ketone X .
- Ketone X gives a yellow precipitate with alkaline I2(aq)\mathrm{I}_{2}(\mathrm{aq}).

How many isomeric ketones could be ketone X ?

A

1

B

2

C

3

D

4

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