Organic Mechanisms (A Level only) (AQA A Level Chemistry)

Exam Questions

3 hours30 questions
1a1 mark

Three reactions of propene are shown in Figure 1. State the name of the mechanism occurring in reactions 1, 2 and 3.

Figure 1

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1b3 marks

A hydration reaction occurs in Reaction 3 when propene is reacted with water at 300 оC in the presence of a phosphoric acid, H3PO4, catalyst at 60 atm.

The first step of the mechanism for this reaction is the carbon carbon double bond attacking a hydrogen ion.

Outline the mechanism for reaction 3.

1c3 marks

Explain why propan-2-ol is formed in Reaction 3 rather than propan-1-ol 

1d2 marks

State the reagents required for Reactions 1 and 2.

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2a1 mark

Figure 1 outlines the separate production of an amine via two different methods from a halogenoalkane. State the name of the mechanism for Reactions 1 and 2.

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2b4 marks

Outline the reaction mechanism for Reaction 2.

2c1 mark

Give one advantage of preparing a primary amine via reactions 1 and 3 rather than via reaction 2.

2d2 marks

The ethylamine produced in Reaction 2 can react with ethanoyl chloride, CH3COCl, to produce an N-substituted amide. Write an equation for this reaction and give the name of the product.

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3a1 mark

Name the mechanism that occurs between water and ethanoyl chloride, CH3COCl

3b4 marks

Complete the mechanism shown in Figure 1 for the reaction between water and ethanoyl chloride.

Figure 1

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3c1 mark

State the name of the other product of the reaction between water and ethanoyl chloride.

3d1 mark

State the name of the product that would be formed in the reaction between ethanoyl chloride and methylamine. 

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4a1 mark

Benzene can react with aluminium bromide, AlBr3, and bromoethane, CH3CH2Br, to form ethylbenzene

Write the equation for the formation of the CH3CH2+ species.

4b1 mark

Name the type of mechanism for the formation of ethylbenzene from benzene and aluminium bromide

4c3 marks

Outline the mechanism for the formation of ethylbenzene.

4d1 mark

State the type of reaction that occurs in part (c). 

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5a1 mark

Figure 1 shows the nitration of compound A

Figure 1

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The reagents for this reaction are concentration nitric acid, HNO3 (aq), and concentrated sulfuric acid, H2SO4 (aq). Write an equation for the formation of the nitronium ion which acts as the electrophile.

5b3 marks

Outline the mechanism for the reaction that occurs in part (a).

5c1 mark

State the reagent required for the conversion of compound B and compound C as shown in Figure 2.

Figure 2

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5d4 marks

Figure 3 shows the dehydration of the alcohol group in compound C in acidic conditions.
Outline the mechanism for the conversion of compound C to compound D. You should use H+ to represent the acid in your mechanism. 

Figure 3

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1a1 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.

1b1 mark

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

1c4 marks

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

Outline the mechanism for the reaction.

1d2 marks

Suggest why carbonyl compounds are likely to undergo nucleophilic attack.

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2a2 marks

This question is about the reactions of carbonyl compounds.

Pentan-2-one is reduced using sodium borohydride, NaBH4, followed by dilute hydrochloric acid in a two-step reaction.

Write an equation to show the reaction which takes place during the reduction of pentan-2-one and give the IUPAC name of the product formed.

[H] should be used to represent NABH4 in the equation.

2b2 marks

In the reaction between pentan-2-one and NaBH4 a hydride ion is involved.

Give the formula of a hydride ion and suggest its role in the reaction.

2c5 marks

Outline the mechanism between pentan-2-one and NaBH4.

2d5 marks

The product formed in part (c) is optically inactive. Explain why.

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3a2 marks

Acylation reactions are used in many industries including pharmaceuticals and textiles.            

i)
Complete the following equation shown in Figure 1 for the acylation of propan-1-ol, CH3CH2CH2OH, with ethanoic anhydride.
ii)
Name the organic product.

Figure 1

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3b3 marks

Although acid anhydrides have a slower rate of reaction than acyl chlorides they generally make better acylation agents than acyl chlorides.

Give 3 reasons why.

3c6 marks

Ethanoyl chloride and propylamine react together to produce a primary amide.

i)
Name the mechanism between ethanoyl chloride and propylamine.

ii)
Outline the mechanism for the reaction between ethanoyl chloride and propylamine.
Name the product.

3d4 marks

Butan-2-ol also undergoes a nucleophilic addition-elimination reaction with ethanoyl chloride.

Outline the mechanism for the reaction

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4a2 marks

Tetrabutylammonium chloride (Figure 1) is an example of a cationic surfactant with many uses, including a type of chromatography known as ion-pair chromatography.

Name this type of compound and give the skeletal formula of the compound shown in Figure 1.

Figure 1

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4b2 marks

Tetrabutylammonium chloride is made by a reaction involving a halogenoalkane.

State the reaction conditions and name the type of mechanism involved in this reaction.

4c4 marks

Propylamine is a colourless liquid with a fishy ammonia-like odour. Its main use is in chemical manufacture.

Outline a mechanism for the reaction of ammonia with 1-chloropropane, to form propylamine, CH3CH2CH2NH2.

4d5 marks

Ethylamine can react with bromoethane to produce a compound with a molecular formula of C4H11N.

Outline the mechanism for the reaction and name the organic product which is formed.

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5a4 marks

This question is about the reactions of aromatic compounds.

Explosives and dyes are produced by a reaction which involves nitrating a benzene ring.

i)
Name the type of reaction mechanism taking place when benzene is nitrated

ii)
Give the reagents and conditions for the reaction.

iii)
Give the equation for the production of the nitronium ion, used in the nitration reaction.
5b3 marks

Give the mechanism for the reaction between benzene and the nitronium ion to produce nitrobenzene.

5c4 marks

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.

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

ii)
Outline the mechanism for the reaction of the electrophile with benzene to produce 1-phenylethanone.
5d5 marks

Phenylamine reacts with bromoethane to produce a secondary amine, N-ethyl-N-phenylamine.

Outline the mechanism for the reaction and suggest how the conditions can be controlled to reduce further substitution on the amine.

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1a6 marks

Outline the mechanism for the formation of N-ethyl propanamide using an appropriate acyl chloride and amine.

1b1 mark

State the name of the mechanism required in part (a)

1c5 marks

Outline the mechanism for the reaction of the acid chloride used in part (a) and propan-1-ol.

1d2 marks

Suggest one disadvantage of the reaction in part (c) and suggest an improvement.

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2a2 marks

The preparation of a common ‘over the counter drug’ is outlined in Figure 1. This reaction occurs in the presence of a few drops of concentrated sulfuric acid.

Figure 1

1-20

           

Give the IUPAC names of Compounds A and B

2b4 marks

Using Figure 1 in part (a), suggest a mechanism for the formation of Compound C.

2c3 marks

Suggest why ethanoic anhydride is used in the preparation of Compound C instead of ethanoyl chloride.

2d1 mark

Draw the structure of the product from the reaction between Compound A and methanol in the presence of a few drops of concentrated sulfuric acid.

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3a2 marks

Figure 1 shows the formation of a ketone via electrophilic substitution. Outline the mechanism to show the formation of the catalyst and electrophile responsible for this reaction.

Figure 1

2-19

 

3b5 marks

Outline the mechanism for the formation of the ketone, including the regeneration of the catalyst required.

3c2 marks

Outline the mechanism for the conversion of Compound X to Compound Y if sodium tetrahydridoborate, NaBH4, is used as the reducing agent.

           
Figure 1

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3d1 mark

Name the product of the reaction between Compound Z and lithium aluminium hydride LiAlH4

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4a1 mark

The reversible reaction for the formation of an ester is shown in Figure 1.

Figure 1

4-18 

An example of an ester is propyl ethanoate. State the type of mechanism that occurs when this ester is hydrolysed in alkaline conditions.

4b2 marks

Using propyl ethanoate as an example, outline the mechanism for the hydrolysis reaction that takes place in alkaline conditions.

Please note you do not need to show the deprotonation step.

4c3 marks

An ester can be formed from one molecule. Figure 1 shows the formation of a cyclic ester from 5-hydroxypentanoic acid. Step one of the mechanism is the protonation of the oxygen atom in the C=O and step two is the cyclisation of the molecule.

Suggest a mechanism to show these two steps.

Figure 1

5-17

4d2 marks

The final step to this mechanism is deprotonation of the molecule. Using Figure 2, suggest a mechanism for the formation of intermediate C from B.

Figure 2

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5a1 mark

Name the amine which has the formula (CH3CH2)2NH

5b3 marks

Outline the mechanism to show the reaction between (CH3CH2)2NH reacts with a small excess of chloromethane, CH3Cl.

5c2 marks

Draw and name the product of the reaction between a large excess of chloromethane and (CH3CH2)2NH.

5d2 marks

Write two equations to show the reaction of CH3CH2NH2 and ethanoic anhydride. 

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