AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Nucleophilic properties (A-level only): Amines are nucleophiles.
A nucleophile is an electron pair donor that is attracted to an atom carrying a partial positive charge.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 1 of 5
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A nucleophile is an electron pair donor that is attracted to an atom carrying a partial positive charge. An amine has exactly what that requires: a lone pair sitting on the nitrogen atom, ready to form a new bond. It is the same lone pair that makes the amine a base, and the only difference is what it attacks. Offered a proton, the amine behaves as a base; offered a δ⁺ carbon, such as the carbon bonded to a halogen in a halogenoalkane or the carbonyl carbon of an acyl chloride, it behaves as a nucleophile. Anything that makes the lone pair more available makes the amine both a stronger base and a better nucleophile, which is why aliphatic amines outperform phenylamine in both roles.
What earns the marks
- Defining a nucleophile as an electron pair donor.
- Identifying the lone pair on nitrogen as the pair that is donated.
- The attack being at a carbon atom carrying a δ⁺ charge.
- Linking nucleophile strength to the same lone pair availability that controls base strength.
Common mistakes and how to put them right
Saying the amine is attracted to the halogen atom rather than to the δ⁺ carbon.
Drawing the curly arrow from an N-H bond rather than from the lone pair.
Calling an amine an electrophile because it contains hydrogen atoms.
Claiming a nucleophile must carry a full negative charge.
Exam tips
- In any amine mechanism the first arrow starts at the lone pair on the nitrogen; draw the lone pair in before you draw the arrow.
- If a question asks why phenylamine is a poorer nucleophile, reuse the base strength argument word for word.
Try the lesson
The start of the Nucleophilic properties (A-level only): Amines are nucleophiles. lesson, made from checked teaching notes for this specification point.
Have a go first
Which feature of an amine molecule allows it to act as a nucleophile?
Listen
A nucleophile is an electron pair donor that is attracted to an atom carrying a partial positive charge. An amine has exactly what that requires: a lone pair sitting on the nitrogen atom, ready to form a new bond. It is the same lone pair that makes the amine a base, and the only difference is what it attacks. Offered a proton, the amine behaves as a base; offered a δ⁺ carbon, such as the carbon bonded to a halogen in a halogenoalkane or the carbonyl carbon of an acyl chloride, it behaves as a nucleophile. Anything that makes the lone pair more available makes the amine both a stronger base and a better nucleophile, which is why aliphatic amines outperform phenylamine in both roles. A strong answer earns marks for these points. defining a nucleophile as an electron pair donor. identifying the lone pair on nitrogen as the pair that is donated. the attack being at a carbon atom carrying a δ⁺ charge. linking nucleophile strength to the same lone pair availability that controls base strength. Exam tip: In any amine mechanism the first arrow starts at the lone pair on the nitrogen; draw the lone pair in before you draw the arrow.
See it
Key words
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nucleophile
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lone pair on nitrogen
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attack at a δ⁺ carbon
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See every definition
- nucleophile
- An electron pair donor that is attracted to an atom carrying a partial positive charge.
- lone pair on nitrogen
- The pair sitting on the nitrogen atom that is ready to form a new bond.
- attack at a δ⁺ carbon
- Behaving as a nucleophile when offered a carbon carrying a partial positive charge, such as in a halogenoalkane or an acyl chloride.
Label the diagram
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