Extending Carbon Chains (OCR A Level Chemistry)

Exam Questions

2 hours27 questions
1a4 marks

This question is about the formation of nitrile compounds.

Propanenitrile can be formed from a haloalkane via a substitution reaction.

i)
Suggest a suitable haloalkane to form propanenitrile.
[1]
ii)
State the reagent and conditions required to form a nitrile from a haloalkane. 
[3] 

 

1b3 marks

Using 'curly arrows' describe the mechanism for the formation of propanenitrile from a haloalkane. Include relevant dipoles in your mechanism. 

1c3 marks

An alternative method of forming nitrile compounds is via the nucleophilic addition of a carbonyl compound. 

Complete the nucleophilic mechanism below using curly arrows for the formation of 2-hydroxypropanenitrile.

6-7_q1c-ocr-a-as--a-level-easy-sq

1d1 mark

State the IUPAC name of the nitrile formed when propanone reacts with aqueous potassium cyanide and sulfuric acid.

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2a2 marks

This question is about the reaction of nitriles.

Nitriles can undergo hydrolysis by dilute acid and by dilute alkali. 

Write the equation for the reaction of hydrolysis of propanenitrile, CH3CH2CN, by dilute hydrochloric acid.

2b1 mark

The hydrolysis of propanenitrile using dilute sodium hydroxide requires two steps, the first step forms sodium propanoate and ammonia. Suggest reagents for the second step.

2c1 mark

Propanenitrile can be reduced to form propylamine. Suggest a suitable reducing agent.

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3a1 mark

In the Friedel-Crafts acylation reaction, an acyl group is substituted into the benzene ring.

State the IUPAC name of the compound formed when benzene reacts with propanoyl chloride in the presence of aluminium chloride.

3b1 mark

State the name of the mechanism that will take place in the reaction outlined in part (a). 

3c4 marks

Using 'curly arrows' describe the mechanism for the reaction outlined in part (a).

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4a2 marks

4-methylphenylamine can be formed in three steps from benzene.

6-7_q4a-ocr-a-as--a-level-easy-sq

Step 1 requires bromomethane and iron(III) bromide. State the IUPAC name of compounds A and B

4b4 marks

Using ‘curly arrows’ describe the mechanism for step 1. 

4c3 marks

State suitable reagents for step 3.

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1a2 marks

Ethylbenzene, C6H5CH2CH3, is an important chemical intermediate in the manufacture of polystyrene, pesticides, rubber, paint and inks.

The synthesis of ethylbenzene can occur via Friedel-Crafts alkylation using ethene, hydrogen chloride, benzene and an aluminium chloride, AlCl3, catalyst. 

Name the mechanism for the reaction of ethene and hydrogen chloride.

Write an equation for the subsequent formation of the carbocation that reacts with benzene to produce ethylbenzene.

1b3 marks

Outline the mechanism for the reaction of benzene with the carbocation that was formed in part (a).

1c2 marks

1-methylpropylbenzene, C6H5CH(CH3)CH2CH3 is the major organic product formed when benzene and but-1-ene react together in the presence of aluminium bromide and hydrogen bromide. Write an equation showing the formation of the electrophile required for this reaction. 

1d2 marks

Explain why a minor product of butyl benzene, C6H5CH2CH2CH2CH3, is produced in this reaction. 

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2a1 mark

Propanal reacts with potassium cyanide, followed by dilute acid, to form the hydroxynitrile CH3CH2CH(OH)CN.

Give the IUPAC name of CH3CH2CH(OH)CN. 

2b1 mark

Name the mechanism for the reaction between potassium cyanide and propanal.

2c4 marks

Propanone undergoes the same reaction with HCN as propanal to form a hydroxynitrile.

Outline the mechanism for the reaction.

2d2 marks

Suggest why carbonyl compounds are likely to undergo nucleophilic attack. 

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3a1 mark

Benzene is a useful in the production of pharmaceuticals, however due to the stability of the benzene ring it is fairly unreactive with electrophiles. Instead stronger electrophiles can be made by using a halogen carrier such as aluminium chloride, AlCl3 with ethanoyl chloride. 

Give an equation to show the generation of an electrophile using aluminium chloride.

3b3 marks

Outline the mechanism for the reaction of the electrophile with benzene to produce 1-phenylethanone.

3c2 marks

Outline the mechanism for the reaction of the ethanoyl chloride with the catalyst to form the acylium ion needed for electrophilic substitution.

3d2 marks

Aluminium chloride is used as the catalyst in the reaction between benzene and ethanoyl chloride. Explain how the catalyst reforms.

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4a3 marks

A reaction pathway to produce a carboxylate salt, Compound M, which contains three carbon atoms is shown below.

Bromoethane → Compound L → Compound M

Give the correct reagents to form compound L from bromoethane.

4b4 marks

Name and outline the mechanism for the formation of Compound L from bromoethane.

4c2 marks

State the reagents required for the formation of Compound M from Compound L and give an equation for the reaction.

4d2 marks

A chemist reacted Compound L with hydrogen gas in the presence of a nickel catalyst. Name and draw the structure of the compound produced.

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1a5 marks

Compounds A and B can be formed in the reaction scheme shown in Figure 1.

Compound B is a primary amine with the molecular formula C7H17N

Figure 1

6-7_q1a-ocr-a-as--a-level-hard-sq

Explain how compounds A and B can be formed. In you answer include required reaction conditions and regents as well as the structure of compounds A and B

1b2 marks

State the IUPAC names for compounds A and B.

1c3 marks

Using curly arrows, describe the mechanism for the reaction 1.

1d6 marks

Compound A can be hydrolysed via two methods. 

Explain how compound A can be hydrolysed. In your answer include relevant equations.

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2a2 marks

Propylamine, shown in Figure 1, can be synthesised from ethene.


Figure 1

7-3

A student suggests that ethene should be reacted with hydrogen cyanide to produce propylamine.

 

Figure 2 shows the outline of a reaction scheme to convert ethene into propylamine.

Figure 2

Ethene rightwards arrow with Step space 1 on top Compound rightwards arrow with Step space 2 on top Compound B rightwards arrow with Step space 3 on top Propylamine

Identify which step of the reaction scheme could use the student’s suggestion of hydrogen cyanide. Justify your answer.

2b2 marks

Draw the skeletal structure of compound A, from part a), and state the reagents required for its formation.

2c2 marks

The final step of the reaction scheme will form the desired amine.

i)
State the IUPAC name of compound B.
[1]
ii)
Identify the type of reaction that compound B undergoes to form propylamine. Justify your answer.
[1]

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3a2 marks

Benzene undergoes a substitution reaction to form compounds X and Y. This is shown in Figure 1.

Figure 1

6-7_q3a-ocr-a-as--a-level-hard-sq

State the formulas of the reagents required for reaction 1.

3b3 marks
Propene will react with benzene in the presence of aluminium chloride and hydrogen chloride to form compound Y



Using curly arrows, describe the mechanism which will generate the electrophile.

3c4 marks

Using curly arrows, describe the mechanism for the formation of compound Y. In your answer show how AlCl3 is regenerated. 

3d1 mark

State the type of reaction that occurs in both reactions in part a).

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4a4 marks

Lactic acid, CH3CH(OH)COOH, can be formed from compound X in three steps as shown below.

Compound X rightwards arrow with Step space 1 on top Ethanal rightwards arrow with Step space 2 on top Compound Y rightwards arrow with Step space 3 on top Lactic acid

Compound X undergoes oxidation to form ethanal. 

i)
State the IUPAC name for compound X.
[1]
ii)
Draw the apparatus which is required for step 1.
[3]

4b4 marks

Using curly arrows, describe the mechanism for step 2.

4c1 mark

State the reagents required for step 3.

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