A2 LEVEL CHEMISTRY

AMINES
AMINO ACIDS AND CHIRALITY
POLYESTERS AND POLYAMIDES
SYNTHESIS

TEST

Answer all questions
Max 59 marks

	
Name		…………………………………………………………..

Mark		……../59	……....%	Grade ………

1.	Compound A, shown below, is being considered as an azo dye by a chemical company. A chemist planned a two-stage synthesis of compound A starting from an aromatic amine.
		
	The aromatic amine is first converted into a diazonium ion.
•	Draw the displayed formula of the aromatic amine and of the diazonium ion.
•	State the reagents and conditions for each stage in the synthesis of compound A from an aromatic amine.

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[Total 5 marks]

2.	
α-amino acid	R group	
glycine	H	
leucine	CH2CH(CH3)2	
isoleucine	CH(CH3)CH2CH3	
alanine	CH3	
valine	CH(CH3)2	
lysine	(CH2)4NH2	
glutamic acid	(CH2)2COOH	
	α-Amino acids form different ions at different pH values. Zwitterions are formed when the pH is equal to the isoelectric point of the α-amino acid.
	The isoelectric points of three α-amino acids are given below:
	alanine, pH = 6.0	glutamic acid, pH = 3.2	lysine, pH = 9.7
	Draw the structures of the ions formed by these α-amino acids at the pH values below. Refer to the table above.

alanine at pH = 6.0	glutamic acid at pH = 10	lysine at pH = 2.0	

			
[Total 3 marks]

3.	
α-amino acid	R group	
glycine	H	
leucine	CH2CH(CH3)2	
isoleucine	CH(CH3)CH2CH3	
alanine	CH3	
valine	CH(CH3)2	
lysine	(CH2)4NH2	
glutamic acid	(CH2)2COOH	
	α-Amino acids can react to form polypeptides.
	A short section of a polypeptide is shown below.
		
	Name the α-amino acid sequence in this section of the polypeptide. Refer to the table above.
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[Total 1 mark]

4.	The four amino acids shown below are found in proteins and enzymes.

	Write down the structural formula for a dipeptide formed from one molecule of glycine and one of lysine.

[Total 2 marks]

5.	Leucine (2-amino-4-methylpentanoic acid) is a naturally occurring α-amino acid that is often used in protein supplements.
	Leucine has a structural formula of (CH3)2CHCH2CH(NH2)COOH.
(a)	(i)	State the general formula of an α-amino acid.
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[1]
(ii)	Draw a displayed formula of leucine.

[1]
(b)	Leucine can exist as a zwitterion.
(i)	State what is meant by the term zwitterion.
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[1]
(ii)	Explain with the aid of a diagram how the zwitterion is formed from the functional groups in leucine.

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[2]
(c)	Leucine can be obtained from a source of protein such as meat.
(i)	State suitable reagents and conditions to break down a protein into amino acids.
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[2]
 (ii)	State the type of reaction occurring.
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[1]
[Total 8 marks]

6.	One of the final stages in winemaking involves the fermentation of malic acid to lactic acid.
	An equation for the reaction is shown below.

	Both acids contain a chiral centre.
(i)	Identify the chiral centre on the structure of malic acid above using an asterisk *.
[1]
(ii)	Draw a diagram to show the 3-D arrangement of groups around the chiral centre in malic acid.

[1]
[Total 2 marks]

7.	Geraniol, C9H15CH2OH, is a naturally occurring compound that contributes to the smell of roses. The skeletal formula of geraniol is shown below.
		
		geraniol
(a)	Name the two different functional groups in geraniol.
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[1]
(b)	Geraniol has stereoisomers due to one of the double bonds in the molecule.
(i)	What is meant the term stereoisomer?
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[1]
(ii)	Name the type of stereoisomerism shown by geraniol.
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[1]
(iii)	State how this type of stereoisomerism arises in organic molecules.
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[1]
(iv)	Explain why one of the double bonds in geraniol does not give rise to stereoisomerism.
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[1]
[Total 5 marks]

8.	Kevlar is a very tough polymer made from 1,4-diaminobenzene and benzene-1,4-dicarboxylic acid.
(i)	State a use for Kevlar.
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[1]
(ii)	Describe the polymerisation reaction that forms Kevlar. Include in your answer:
•	an explanation of the type of polymerisation involved
•	an equation for the reaction
•	a repeat unit to show the structure of Kevlar.

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[5]
[Total 6 marks]

9.	Short sections of the molecular structures of two polymers are shown below.

(a)	(i)	Circle, on the diagrams above, the simplest repeat unit in each polymer.
[2]
(ii)	In the boxes below, draw the displayed formulae of the two monomers that could be used to prepare polymer D.
		
[2]
(b)	Chemists have developed degradable polymers to reduce the quantity of plastic waste being disposed of in landfill sites. Polymer D is more likely to be a ‘degradable polymer’ than polymer C.
	Suggest two reasons why.
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[2]
[Total 6 marks]

10.	Aspirin and paracetamol are commonly available painkillers.

	Name the functional groups in aspirin and in paracetamol.
	aspirin .................................................................................................................
	paracetamol ........................................................................................................
[Total 2 marks]

11.	A student carried out some reactions with samples of aspirin and paracetamol in the laboratory. Their structures are below.

 	The student tried to react each of the reagents A, B and C with aspirin and paracetamol.
•	Reagent A reacted with aspirin and with paracetamol.
•	Reagent B reacted only with aspirin.
•	Reagent C reacted only with paracetamol.
	Suggest possible identities of reagents A, B and C and the organic products that would be formed.
(i)	Reagent A: ........................................................................................................
	Organic product with aspirin:

	Organic product with paracetamol:

[3]
(ii)	Reagent B: ........................................................................................................
	Organic product with aspirin:

[2]
(iii)	Reagent C: ........................................................................................................
	Organic product with paracetamol:

[2]
[Total 7 marks]
12.	Noradrenaline is produced naturally by nerve cells in the brain. Compound P is a synthetic compound that has been widely used as an appetite suppressant. It is thought to be effective because it is similar to noradrenaline.

(a)	(i)	Suggest a reagent that could be used in a test to distinguish compound P from noradrenaline.
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[1]
(ii)	Draw a ring round the functional group responsible for the positive result in the test you have chosen.
[1]
(iii)	State the expected observation for the positive result in the test you have chosen.
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[1]
 (b)	Both these compounds have stereoisomers due to the presence of chiral centres.
(i)	Identify the chiral centres in each molecule by labelling them clearly with asterisks (*) on the structures above.
[2]
(ii)	State the type of stereoisomerism caused by the presence of chiral centres.
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[1]
(iii)	Using noradrenaline as an example, explain how a chiral centre gives rise to the stereoisomers. Illustrate your answer with a suitable diagram of the stereoisomers.
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[3]

(c)	Explain why a pharmaceutical company may produce an appetite suppressant containing only one stereoisomer of compound P, rather than a mixture of the stereoisomers.
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[3]
[Total 12 marks]