INTERNATIONAL A-LEVEL

CHEMISTRY (9620)

Unit 4: Organic 2 and Physical 2

This question is about three isomers of C4H8O

Give the IUPAC name for isomer B and for isomer C.

[2 marks]

B

C

Isomers A and B both react with KCN followed by dilute acid.

Name the mechanism for this reaction.

Draw the two enantiomers formed by isomer A in this reaction and show how the two enantiomers are related to each other.

[3 marks]

Mechanism

Enantiomer 1                                                       Enantiomer 2

Describe a test-tube reaction to distinguish isomer C from isomer A.

State the observations.

[2 marks]

Test

Observation(s) with isomer A

Observation(s) with isomer C

Aspirin can be produced by the acylation of 2-hydroxybenzoic acid (salicylic acid), as shown in Figure 1. In this reaction, ethanoyl chloride is a powerful acylating agent.

Figure 1

In the industrial manufacture of aspirin, ethanoic anhydride is used instead of ethanoyl chloride as the acylating agent.

Give two reasons why ethanoic anhydride is used instead of ethanoyl chloride.

[2 marks]

Reason 1

Reason 2

In the laboratory, the aspirin produced is impure. It is purified by recrystallisation using water as the solvent.

Complete the steps carried out in a recrystallisation practical.

[3 marks]

Step 1

Step 2      Filter whilst hot

Step 3

Step 4      Vacuum filter

Step 5

Step 6      Dry in a desiccator

Outline how you could confirm that a sample of aspirin is pure.

[2 marks]

Ethanoyl chloride reacts with amines to produce amides.

Name and outline the mechanism for the reaction between ethanoyl chloride and methylamine.

[5 marks]

Name of mechanism

Amines can be prepared from different compounds.

Propylamine (CH3CH2CH2NH2) can be prepared in two different one-step reactions.

For each reaction, identify:

• the organic starting material, and

• the reagent and condition(s).

[4 marks]

Reaction 1

Organic starting material

Reagent and condition(s)

Reaction 2

Organic starting material

Reagent and condition(s)

Gas chromatography (GC) was used to separate a mixture of five compounds, D, E, F, G and H.

Table 1 shows the names and formulae of these compounds.

Table 1

Figure 2 shows the output from the detector in this separation.

Figure 2

State the meaning of the term retention time.

[1 mark]

Two of the compounds are present in the mixture in equal amounts.

Explain how Figure 2 shows this.

[1 mark]

Give a reason why nitrogen is used rather than oxygen as the carrier gas.

[1 mark]

Polyethane-1,2-diol (PEG) is a liquid and is part of the stationary phase.

Identify what else is needed to complete the stationary phase.

Tick () one box.

[1 mark]

Aluminium oxide

Argon

Carbon dioxide

Epoxyethane

Polyethane-1,2-diol (PEG) can be represented as

H – [O – CH2 – CH2]n – O – H

Explain why PEG is polar.

[2 marks]

Deduce the compound in the mixture with retention time 4.9 minutes.

Give a reason for your choice.

[2 marks]

Compound

Reason

Some modifications to the GC apparatus were considered to improve the separation of the same mixture of components.

Predict the effect, if any, of each modification on the retention times of the components.

[3 marks]

Increasing the column temperature

Decreasing the column length

Decreasing the carrier gas flow rate

Clothes are often made from polyesters such as Terylene.

Two repeating units of the polymer Terylene are shown.

Draw the skeletal formulas of the two monomers that react to form. Terylene.

[2 marks]

Monomer 1                                    Monomer 2

Explain why Terylene is biodegradable but polychloroethene is not.

[3 marks]

Proteins are chains of amino acids linked together.

The structure of a tripeptide is

Draw a circle around one peptide link on the diagram.

[1 mark]

Draw the displayed formula of the zwitterion formed by the amino acid which makes up the central section of the tripeptide in Question 04.3.

[1 mark]

Name the type of structure where protein chains form. α-helixes and β-pleated sheets.

[1 mark]

Name the interactions that hold protein chains in a β-pleated sheet.

Explain how these interactions are formed.

[3 marks]

Cisplatin is used as an anticancer drug.

Cisplatin bonds with DNA by ligand replacement.

Figure 3 shows part of a DNA strand.

Complete Figure 3 to show the complex formed when one molecule of cisplatin binds with the part of DNA shown.

[1 mark]

Figure 3

State how cisplatin affects cancer cells.

[2 marks]

The molecule cyclohexa-1,3,5-triene does not exist and is described as theoretical.

State and explain the stability of benzene compared with the theoretical cyclohexa-1,3,5-triene.

Use the following data.

[4 marks]

Benzene can be converted into phenylamine by a two-step synthesis as shown.

The mechanism of Reaction 1 involves attack by an electrophile.

Give the reagents used to produce the electrophile needed in Reaction 1.

[2 marks]

The percentage yield of the two-step synthesis where benzene is converted into phenylamine was found to be 68%.

State the two measurements that need to be recorded to calculate the percentage yield.

[2 marks]

Measurement 1

Measurement 2

Explain why phenylamine is a weaker base than hexylamine.

[2 marks]