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.
Amines E, F and G are weak bases.
Explain the difference in base strength of the three amines and give the ord... 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.
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Answer
The base strength of amines largely depends on the availability of the lone pair of electrons on the nitrogen atom.
Amine E is least basic because it has no electron-donating groups attached to the ring, making the nitrogen's lone pair less available to accept protons. The presence of the aromatic ring also stabilizes the lone pair through resonance.
Amine F has a substituent (-CH2-NH2) that donates electron density towards the nitrogen. This increases the availability of the lone pair compared to E but not as much as G.
Amine G has an even stronger electron-donating group (-NH2) directly attached, which significantly increases the basicity of the nitrogen.
Thus, the order of increasing base strength is: E < F < G.
Step 2
Suggest the structures of the two intermediate compounds.
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Answer
Intermediate compounds can be suggested as follows:
First Intermediate: C6H5-CH2-NH2 (Phenylmethylamine)
Second Intermediate: C6H5-CH(CH3)-NH2 (N-Methylphenethylamine)
Step 3
Step 1: Give reagents and conditions for the first step.
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For Step 1:
Reagents: Br2, UV light (for bromination of methylbenzene)
Conditions: Photochemical conditions under UV light are required to initiate the reaction.
Step 4
Step 2: Give reagents and conditions for the second step.
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For Step 2:
Reagents: KCN, alcoholic NaOH
Conditions: The reaction should occur under alcoholic conditions to ensure proper nucleophilic substitution.
