AQA A Level Chemistry
AQA A Level Chemistry 3.3.11 Amines Exam Questions
Free AQA A Level Chemistry exam questions for 3.3.11 Amines, with a mark scheme for every pack. Covers classifying amines, preparation of aliphatic and aromatic amines, base strength, quaternary ammonium salts and nucleophilic reactions of amines.
3.3.11 Amines exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA A Level Chemistry 3.3.11 Amines
Amines are organic derivatives of ammonia, and on the AQA A Level course you study their structure, preparation, basicity and reactions. You need to classify amines and quaternary ammonium salts, prepare aliphatic amines from halogenoalkanes or by reducing nitriles, and prepare aromatic amines by reducing nitrobenzene. You compare the base strength of ammonia, primary aliphatic amines and phenylamine using the availability of the nitrogen lone pair, and describe amines as nucleophiles reacting with halogenoalkanes and with acyl chlorides or acid anhydrides. The topic connects 3.3.3 Halogenoalkanes, 3.3.9 acylation and 3.3.10 nitration. Examiners favour base strength explanations and synthesis steps.
What you need to know
- Classification Primary, secondary and tertiary amines have one, two and three alkyl or aryl groups on the nitrogen. Quaternary ammonium ions have four, e.g. (CH3)4N+. Quaternary ammonium salts with long chains are cationic surfactants used in fabric softeners and hair conditioners.
- Preparing aliphatic amines React a halogenoalkane with excess ammonia, which gives a mixture of amines. Alternatively, reduce a nitrile with LiAlH4 or with H2 and a nickel catalyst, which gives only the primary amine.
- Preparing aromatic amines Nitrate benzene, then reduce nitrobenzene with tin and concentrated hydrochloric acid followed by NaOH: C6H5NO2 + 6[H] → C6H5NH2 + 2H2O. Aromatic amines are used to make dyes.
- Base strength Amines are bases because the nitrogen lone pair accepts a proton. Primary aliphatic amines are stronger bases than ammonia because alkyl groups push electron density onto N. Phenylamine is weaker than ammonia because the lone pair is delocalised into the benzene ring.
- Nucleophilic reactions Amines react with halogenoalkanes by nucleophilic substitution to give secondary and tertiary amines and quaternary ammonium salts. They react with acyl chlorides and acid anhydrides by addition-elimination to give N-substituted amides.
Common mistakes in 3.3.11 Amines
- Saying phenylamine is a stronger base because of the benzene ring. The ring delocalises the lone pair, making it less available, so phenylamine is weaker.
- Giving the wrong reducing agent for nitrobenzene. Use tin and concentrated hydrochloric acid, then sodium hydroxide.
- Forgetting that reducing a nitrile keeps the extra carbon, e.g. propanenitrile gives propylamine (propan-1-amine).
- Describing quaternary ammonium ions as bases. They have no lone pair on nitrogen, so cannot accept a proton.
- Not mentioning that excess ammonia gives a mixture of products and lowers the yield of the primary amine.
Try three 3.3.11 Amines exam-style questions
1. Explain why ethylamine is a stronger base than ammonia, and phenylamine is a weaker base than ammonia. (4 marks)
Show the mark scheme answer
The base strength depends on the availability of the lone pair on N to accept a proton; the ethyl group pushes electron density onto N, so its lone pair is more available; in phenylamine the lone pair on N is delocalised into the benzene ring; so it is less available to accept a proton.
2. Write an equation for the reduction of nitrobenzene to phenylamine using [H], and give the reagents used. (2 marks)
Show the mark scheme answer
C6H5NO2 + 6[H] → C6H5NH2 + 2H2O; tin and concentrated hydrochloric acid (followed by sodium hydroxide).
3. Explain why reducing propanenitrile is a better way to make propylamine than reacting 1-bromopropane with ammonia. (2 marks)
Show the mark scheme answer
Reaction with ammonia gives a mixture of primary, secondary and tertiary amines and a quaternary salt, because the amine product is also a nucleophile; reduction of the nitrile gives only the primary amine, so the yield is higher and separation is easier.
3.3.11 Amines FAQs
What does AQA A Level Chemistry 3.3.11 Amines cover?
It covers classifying amines and quaternary ammonium salts, preparing aliphatic and aromatic amines, comparing base strength, and the nucleophilic reactions of amines.
Which paper is 3.3.11 Amines examined in?
It is examined in Paper 2, and Paper 3 can also test it.
How do I explain base strength for amines?
Always start from the lone pair on nitrogen and how available it is to accept a proton. Then explain the effect of the attached group: alkyl groups push electrons towards N, while a benzene ring draws the lone pair into delocalisation.
