Condensation Polymerisation (Cambridge (CIE) A Level Chemistry): Exam Questions

Valylalanine, shown in Fig. 1.1, is a dipeptide.

Fig. 1.1

Valylalanine is heated under reflux with dilute hydrochloric acid. Two organic products are formed.

Draw the structural formula of one of these organic products.

Fig. 1.2 shows a dipeptide synthesised from the amino acids cysteine and tryptophan.

Fig. 1.2

Draw the skeletal formula of the amino acid tryptophan.

Polyamides can form strong fibres suitable for weaving. Polyalkenes are generally too weak for this purpose.

Fig. 1.3 shows the structure of serine, an amino acid that forms polyamide links.

Fig. 1.3

Explain why polyamides are suitable for use as weaving fibres but polyalkenes are not. In your answer, refer to the intermolecular forces between the polymer chains.

Explain how the molecule NH₂CH₂CH₂COCl can undergo condensation polymerisation.

Polyurethanes are polymers made by the reaction of a diisocyanate with a diol, as shown in Fig. 2.1. R¹ and R² are hydrocarbon groups.

Fig. 2.1

Lycra^® in Fig. 2.2 is a polyurethane formed from the diisocyanate P and HOCH₂CH₂OH.

Fig. 2.2

i) State the molecular formula of diisocyanate P.

[1]

ii) Draw one repeat unit of Lycra^®. The newly formed linkages must be shown fully displayed.

[2]

Fibres of Lycra^® are strong due to the intermolecular forces between the polymer chains. Complete the table to state two types of intermolecular force responsible for this property, and the groups involved.

State the name of one commercially important example of each of the following types of synthetic polymer.

Synthetic polyamide ..................................................................................................

Synthetic polyester ..................................................................................................

Fig. 2.3 shows the repeat unit of Nylon 66.

Fig. 2.3

Nylon 66 is heated under reflux with dilute sulfuric acid.

Draw the skeletal formulae of the two organic products formed.

Explain how ethane-1,2-diamine acts as a Brønsted–Lowry base.

Construct an equation to show the reaction of ethane-1,2-diamine with an excess of hydrochloric acid.

Ethane-1,2-diamine can react with ethanedioic acid, HOOCCOOH, to form a condensation polymer.

Draw the skeletal formula of the polymer, showing exactly two repeat units. The newly formed linkages must be shown fully displayed.

Fig. 1.1 shows a general dicarboxylic acid and a general diol.

Fig. 1.1

Draw one repeat unit of the polyester formed from these monomers. The newly formed linkage must be shown fully displayed.

In terms of n, state the number of molecules of water formed in the condensation polymerisation of n molecules of a dicarboxylic acid and n molecules of a diol.

Construct an equation for the condensation polymerisation of propanedioyl dichloride and butane-1,4-diol. Your equation should use structural formulae for the monomers and the repeat unit.

State the systematic names of an alternative pair of monomers that could be used to produce the same polymer chain as in (c).

Monomer 1 ..................................................................................................

Monomer 2 ..................................................................................................

Lactic acid has the structural formula CH₃CHOHCOOH.

i) State the names of the two functional groups present in lactic acid.

[1]

ii) State the systematic name of lactic acid.

[1]

iii) State the type of stereoisomerism shown by lactic acid.

[1]

iv) Draw three-dimensional structures for the two stereoisomers of lactic acid.

[1]

Explain how lactic acid can undergo condensation polymerisation.

Poly(lactic acid) is a polyester.

i) Draw a section of the poly(lactic acid) chain showing exactly two repeat units. The newly formed ester linkages must be shown fully displayed.

[1]

ii) State whether the central carbon atom in the repeat unit remains a chiral centre in the polymer. Explain your answer.

[1]

Poly(lactic acid) can also be synthesised from a monomer containing an acyl chloride functional group.

Draw the skeletal formula of this alternative monomer.

State the systematic name of this monomer.

Nomex^® and Kevlar^® are two examples of polyamides containing benzene rings. Nomex^® is made from 1,3-diaminobenzene and benzene-1,3-dicarboxylic acid.

Draw the skeletal formulae of these two monomers.

Draw one repeat unit of the Nomex^® polymer. The newly formed linkages must be shown fully displayed.

Kevlar^® is made from 1,4-diaminobenzene and benzene-1,4-dicarboxylic acid.

Draw two adjacent polymer chains of Kevlar^®, each showing one repeat unit. Clearly show the strongest intermolecular force between the two chains.

State whether Kevlar^® or Nomex^® will have the higher melting point. Explain your answer in terms of the structure of the polymer chains.