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This question is about the three amines, E, F and G - AQA - A-Level Chemistry - Question 11 - 2017 - Paper 2
Question 11
This question is about the three amines, E, F and G. Amine E: Amine F: CH2H2NH2 Amine G: NH(CH2)2CH3 1.1 - Explain the difference in base strength of the three... show full transcript
Worked Solution & Example Answer:This question is about the three amines, E, F and G - AQA - A-Level Chemistry - Question 11 - 2017 - Paper 2
Step 1
Explain the difference in base strength of the three amines and give the order of increasing base strength.
Answer
The base strength of the amines is influenced by the availability of the nitrogen lone pair for protonation.
- Amine E: The lone pair on nitrogen is less available for donation due to the presence of the electron-withdrawing effect from the adjacent aromatic ring, making it the least basic.
- Amine F: This amine has a primary amine structure with NH2, which can effectively donate its lone pair, but it still has some steric hindrance from the additional carbon groups.
- Amine G: With the nitrogen attached to two carbons, it has less inductive withdrawal compared to E and thus is more available to donate its lone pair.
Order of increasing base strength: E < F < G
Step 2
Amine F can be prepared in a three-step synthesis starting from methylbenzene. Suggest the structures of the two intermediate compounds.
Answer
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Intermediate 1: The first intermediate can be achieved by alkylating methylbenzene with bromine (Br), leading to the formation of a corresponding alkyl product (C6H5CH2Br).
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Intermediate 2: In the second step, the product will be reacted further to yield the final amine structure where the alkyl group is now attached to a nitrogen atom (C6H5CH2NH2).