Predicting the Type of Polymerisation — Structured Questions (Cambridge International A-Level Chemistry): Exam Questions

Glycolic acid polymerises to form polyglycolic acid (PGA). The structure of glycolic acid is shown in Fig. 1.1.

Fig. 1.1

State the systematic name of glycolic acid.

Extract:

Glycolic acid polymerises to form polyglycolic acid (PGA). The structure of glycolic acid is shown in Fig. 1.1.

Glycolic acid (HOCH₂COOH) contains two functional groups: a carboxylic acid group (–COOH) and a hydroxyl group (–OH).

State the type of polymerisation involved in the formation of PGA and state the name of the functional group formed between the monomers.

type of polymerisation: ..............................

functional group: ..............................

Extract:

Glycolic acid polymerises to form polyglycolic acid (PGA). The structure of glycolic acid is shown in Fig. 1.1.

Draw a section of the PGA polymer chain showing two repeat units. The ester linkages must be shown fully displayed.

Label one repeat unit on your diagram.

Extract:

State the type of polymerisation involved in the formation of PGA and state the name of the functional group formed between the monomers.

type of polymerisation: ..............................

functional group: ..............................

The type of polymerisation and functional group formed are:

• Type of polymerisation: condensation
• Functional group: ester

State whether PGA is biodegradable. Explain your answer.

Fig. 2.1 shows the structure of dehydroalanine.

Fig. 2.1

State the name of the functional group in dehydroalanine that is not present in most naturally occurring amino acids.

Extract:

Fig. 2.1 shows the structure of dehydroalanine.

Displayed formula of dehydroalanine showing an amino group (–NH₂), a carboxylic acid group (–COOH), and an alkene group (C=CH₂)

Fig. 2.1

Dehydroalanine can undergo addition polymerisation.

Draw one repeat unit of the addition polymer formed by dehydroalanine.

The catalytic hydrogenation of dehydroalanine produces alanine, CH₃CH(NH₂)COOH.

Draw a section of the condensation polymer formed by alanine showing two repeat units. The peptide bond must be shown fully displayed.

Glycine and serine are amino acids with the systematic names 2-aminoethanoic acid and 2-amino-3-hydroxypropanoic acid respectively.

Draw the structural formulae of glycine and serine.

Serine exists as a pair of optical isomers. The three-dimensional structure of one optical isomer is shown in Fig. 3.2.

Fig. 3.2

Draw the three-dimensional structure of the other optical isomer of serine.

Extract:

Glycine and serine are amino acids with the systematic names 2-aminoethanoic acid and 2-amino-3-hydroxypropanoic acid respectively.

Glycine and serine can react to form condensation polymers containing ester and amide linkages.

State the names of the functional groups that react to form:

i) an ester linkage

ii) an amide linkage