This question is about the three amines, E, F and G. Amines E, F and G are weak bases. 1. Explain the difference in base strength of the three amines and give the order of increasing base strength. 2. Amine F can be prepared in a three-step synthesis starting from methylbenzene. Suggest the structures of the two intermediate compounds. For each step, give reagents and conditions only. Equations and mechanisms are not required.

A-Level AQA Chemistry Fundamentals of Acids & Bases: This question is about the three

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. 1. Explain the difference in base strength of the three amines and give the o... 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 an amine depends on the availability of its lone pair of electrons on the nitrogen atom to donate to protons (H+).

Amine E is the strongest base since it is a primary amine with a lone pair that is readily available for donation due to less steric hindrance and low electron-withdrawing effects.
Amine F is a secondary amine. Its lone pair is slightly less available compared to primary amines due to presence of the alkyl group, which can exert an electron-donating inductive effect, but it is still somewhat hindered.
Amine G is the weakest base. The presence of the ethyl group and the additional nitrogen will provide electron repulsion, making it less favorable for the lone pair to accept a proton.

The order of increasing base strength is: G < F < E.

Step 2

Suggest the structures of the two intermediate compounds.

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Answer

The first intermediate compound can be represented as C6H5CH2NH2 (benzylamine).
The second intermediate compound can be represented as C6H5C(Br)(CH3)NH2 (bromobenzylamine).

Step 3

For each step, give reagents and conditions only.

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Answer

Step 1: Reagents - KCN, Conditions - alcoholic & reflux.

Step 2: Reagents - KBr, Conditions - UV light.

This question is about the three amines, E, F and G - AQA - A-Level Chemistry - Question 11 - 2017 - Paper 2

Worked Solution & Example Answer:This question is about the three amines, E, F and G - AQA - A-Level Chemistry - Question 11 - 2017 - Paper 2

Explain the difference in base strength of the three amines and give the order of increasing base strength.

Suggest the structures of the two intermediate compounds.

For each step, give reagents and conditions only.

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