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CAIE A-Level Chemistry AS 13.4 Structural Isomerism and Stereoisomerism Questions

Practise distinguishing structural isomers from stereoisomers and drawing chain, positional, functional, geometrical or optical forms.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • keep the molecular formula fixed while checking whether atom connectivity or only spatial arrangement changes
  • classify different connectivity as chain, positional or functional-group structural isomerism
  • classify identical connectivity with different 3D arrangement as geometrical or optical isomerism

Covered syllabus points

13.4.1—Structural isomerism and its division13.4.2—Stereoisomerism and its division13.4.3—Geometrical (cis/trans) isomerism in alkenes,13.4.4—Chiral centres and enantiomers13.4.5—Chiral centres and geometrical (cis/trans)13.4.6—The possible isomers for an organic molecule

Question 1

[Maximum number: 1]

Compound T has the skeletal formula shown.

compound T

compound T

Which structure is a structural isomer of compound T ?

A
Figure for Question 1 — CAIE A-Level Chemistry AS — Option A
B
Figure for Question 1 — CAIE A-Level Chemistry AS — Option B
C
Figure for Question 1 — CAIE A-Level Chemistry AS — Option C
D
Figure for Question 1 — CAIE A-Level Chemistry AS — Option D

Question 2

[Maximum number: 1]

P and Q are a pair of cis-trans isomers.

What must be the same for P and Q ?
1 their empirical formula
2 their functional groups
3 their skeletal formula

A

1, 2 and 3 are correct

B

1 and 2 only are correct

C

2 and 3 only are correct

D

1 only is correct

Question 3

[Maximum number: 1]

Which alkene shows geometric isomerism?

A

CH3CH2CH2CH=CH2\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}

B

CH3CH2CH=CHCH3\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CHCH}_{3} C

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 react with LiAlH4\mathrm{LiAlH}_{4} to form two optical isomers?

A

CH3CH2COCH3\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COCH}_{3}

B

CH3CH2CH2CHO\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}

C

CH3CH2COCH2CH3\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COCH}_{2} \mathrm{CH}_{3}

D

CH3CH(CH3)CH2CO2H\mathrm{CH}_{3} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H}

Question 5

[Maximum number: 1]

When 1-methylcyclohexene reacts with Br2\mathrm{Br}_{2} the product is X .
When 1-methylcyclohexene reacts with HBr the major product is Y .

Figure for Question 5 — CAIE A-Level Chemistry AS

Which statement is correct?

A

X is a mixture of two stereoisomers; Y does not have stereoisomers.

B

X is a mixture of two stereoisomers; Y is a mixture of four stereoisomers.

C

X is a mixture of four stereoisomers; Y does not have stereoisomers.

D

X is a mixture of four stereoisomers; Y is a mixture of four stereoisomers.

Question 6

[Maximum number: 1]

Structural isomerism and stereoisomerism should be taken into account when answering this question.

The structure of 3-methylcyclobutene is shown.

3-methylcyclobutene

3-methylcyclobutene

A mixture containing all stereoisomers of 3-methylcyclobutene is treated with HBr . This produces a mixture of isomeric bromomethylcyclobutanes.

How many stereoisomers does 3 -methylcyclobutene have, and how many isomeric bromomethylcyclobutanes are present in the product mixture?

3-methylcyclobutene

bromomethylcyclobutanes

2

4

2

6

4

4

4

8

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