Condensation Polymerisation (CIE A Level Chemistry)

Valylalanine shown in Fig. 1.1, is an example of a dipeptide composed of two amino acids, valine and alanine. 

When this compound is placed in acidic conditions, two species are formed. 

Draw one of these two species.  

Fig. 1.1

A dipeptide made from the amino acids cysteine and tryptophan is shown in Fig.1.2 . Cysteine contains a sulphur molecule. 

Fig. 1.2

Draw the structure of the amino acid tryptophan.

Amino acids such as serine shown in Fig. 1.3 will form polyamide links. Polyamides will contain the same type of links and these polymers can be used to form fibres suitable for weaving. Polymers formed from alkenes by additional polymerisation are usually took weak for this purpose.

Fig. 1.3

In terms of intermolecular forces between the polymer chains, explain why polyalkenes are not suitable to be used as fibres for weaving.

Explain why the molecule NH₂CH₂CH₂COCl can form a condensation polymer with itself. 

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.

Fibres of Lycra^® are strong due to the intermolecular forces between the polymer chains. Complete the table to identify two intermolecular forces responsible for this property and the group(s) involved.

Name one example of each of the following types of polymer.

Fig. 2.3 shows the repeat unit of Nylon 66.

Draw the two products from the hydrolysis of Nylon 66.

Ethane-1,2-diamine is a bidentate ligand as well as being a useful reagent in organic chemistry. 

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

Write 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 two repeat units.

Polymers consist of monomers joined together by undergoing either addition or condensation polymerisation.

Fig. 1.1 shows a dicarboxylic acid and a diol that can be used in a general condensation polymerisation reaction.

Fig. 1.1

Draw one repeat unit for this polymerisation.

In terms of n, state the number of molecules of water formed in the condensation polymerisation reaction of a general dicarboxylic acid and a general diol as shown in Fig. 1.1.

Using displayed formulae, write the balanced equation for the condensation polymerisation of the two monomers, propanedioyl dichloride and butane-1,4-diol.

Suggest an alternative pair of monomers that will produce the polymer from part (c).

Lactic acid has the structural formula, CH₃CHOHCOOH.

Poly(lactic acid) is a thermoplastic polyester that can be prepared from lactic acid. It is a renewable material used widely in 3D printers.

Explain why lactic acid can be polymerised.

Polylactic acid contains methyl groups.

Poly(lactic) acid can be prepared using a different monomer.

Draw the skeletal formula of this monomer.

Give the systematic name of another monomer that could make poly(lactic acid).

systematic name ................................................................................

Kevlar ® has a variety of uses, including bulletproof vests and puncture resistant tyres, due to its strength and being lightweight. Nomex ® is most commonly used as a lining of the overalls worn by racing drivers and their pit crews as well as in the personal protective equipment of firefighters due to its flame resistant properties.

Nomex ® is made from 1,3-diaminobenzene and 1,3-benzenedicarboxylic acid.

Draw the skeletal structures of these monomers.

Draw the structure of the Nomex ® polymer.

Kevlar ® is made from 1,4-diaminobenzene and 1,4-benzenedicarboxylic acid.

Draw two repeat units of the polymer to show the strongest intermolecular force in Kevlar ®. 

State whether Kevlar ® or Nomex ® will have the higher melting point. 

Explain your answer.