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CAIE A-Level Chemistry 13.4 Structural and Stereoisomerism

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

13.4 Structural isomerism and stereoisomerism question 1

[Maximum number: 1]

Organic compounds can be distinguished using chemical tests and analytical techniques.

Table 3.1 shows four pairs of organic compounds.

Table 3.1

Table 3.1

A1 and A2 are structural isomers.

Define structural isomers.

13.4 Structural isomerism and stereoisomerism question 2

[Maximum number: 5]

Fig. 4.1 shows a possible synthesis of propene, C3H6\mathrm{C}_{3} \mathrm{H}_{6}.

Fig. 4.1

Fig. 4.1

Question (a)

(a)

Under suitable conditions, propene polymerises to form poly(propene).

Poly(propene) exhibits stereoisomerism.

[ 5 ]

Question (i)

(i)

Define stereoisomerism.

[ 2 ]

Question (ii)

(ii)

Draw a section of poly(propene), showing two repeat units.

Use your diagram to identify the type of stereoisomerism shown by poly(propene). Explain your answer.
section of poly(propene)

[ 3 ]

13.4 Structural isomerism and stereoisomerism question 3

[Maximum number: 4]

Compounds P and Q are structural isomers.

Fig. 4.1

Fig. 4.1

Question (a)

(a)

Define structural isomerism.

[ 2 ]

Question (b)

(b)

P shows geometrical isomerism.

Draw the geometrical isomer of P. Explain why the two isomers are not identical.

Figure for Question (b) — CAIE A-Level Chemistry AS

explanation

[ 2 ]
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