Isomerism: Structural Isomerism & Stereoisomerism (Cambridge (CIE) AS Chemistry): Exam Questions

Table 1.1 shows information about four organic compounds.

Table 1.1

Compound	Displayed formula	Skeletal formula
1. Z-2-chloro-but-2-en-1-ol
2. 2-chloropropanal
3.
4.

Complete Table 1.1.

State the empirical formula of compound 1.

Explain why compound 1 shows geometrical (cis/trans) isomerism but compound 4 does not.

Compounds 2 and 3 both show the same type of stereoisomerism.

i) State the type of stereoisomerism shown by compounds 2 and 3.

[1]

ii) Explain why compound 2 shows this type of stereoisomerism.

[2]

iii) Draw the three-dimensional structures of the two optical isomers of compound 2.

[1]

i) State the systematic name of the unbranched alkane with the fewest carbon atoms that shows structural isomerism.

[1]

ii) State the type of isomerism shown by the isomers in part (i).

[1]

C₄H₈ exists as several isomers.

i) Name the homologous series that C₄H₈ belongs to.

[1]

ii) Draw the skeletal formulae of two cyclic C₄H₈ isomers and two C₄H₈ isomers that show geometrical (cis/trans) isomerism.

[4]

iii) There are two unsaturated C₄H₈ isomers that do not show geometrical (cis/trans) isomerism. Name these isomers and explain why they do not show geometrical (cis/trans) isomerism.

[3]

Draw the displayed formulae of the following compounds and, where appropriate, identify any chiral centres with an asterisk (*).

• 2,4-dimethylhexan-3-ol

• 3-chloro-2,4-dimethylpentane

• 2-aminobutane

Draw the three-dimensional structures of the two optical isomers of 1-bromopropan-1-ol.

Draw the displayed formula of butan-2-ol and the positional isomer of butan-2-ol.

State the systematic names of the two branched-chain structural isomers of butan-2-ol.

Explain why the positional isomer of butan-2-ol does not show stereoisomerism.

The organic compounds in Fig. 1.1 are shown below.

Fig. 1.1

i) State the systematic name of compound A.

[1]

ii) Compound A has two chiral centres.

Draw the three-dimensional structures of one pair of optical isomers of compound A.

[2]

Compounds B, C, D and E all show the same type of stereoisomerism.

On Fig. 1.1, circle the bond(s) in each molecule that are responsible for this isomerism.

Compound D reacts with hydrogen chloride to form two products.

i) Name the mechanism for this reaction.

[1]

ii) One of the products formed exists as a pair of stereoisomers.

Draw the three-dimensional structures of this pair of stereoisomers. Identify the chiral centre with an asterisk (*) on one of your structures.

[3]

Name the type of reaction that occurs when compound E reacts to form methanol and deca-2,4-dienoic acid.