This question is about amines - AQA - A-Level Chemistry - Question 1 - 2019 - Paper 2
Question 1
This question is about amines.
1.1.1
Give an equation for the preparation of 1,6-diaminohexane by the reaction of 1,6-dibromohexane with an excess of ammonia.
1.1.... show full transcript
Worked Solution & Example Answer:This question is about amines - AQA - A-Level Chemistry - Question 1 - 2019 - Paper 2
Step 1
Give an equation for the preparation of 1,6-diaminohexane by the reaction of 1,6-dibromohexane with an excess of ammonia.
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Answer
The balanced equation for the preparation can be written as:
Complete the mechanism for the reaction of ammonia with 6-bromohexylamine to form 1,6-diaminohexane.
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Answer
The mechanism includes the following steps:
Nucleophilic attack of ammonia on the carbon attached to bromine.
Formation of a tetrahedral intermediate, leading to the displacement of bromide.
Deprotonation step that leads to formation of 1,6-diaminohexane as the product.
The cyclic secondary amine that can be formed as a by-product is:
extCyclicsecondaryamine:C5H10N
Step 3
Stage 1 reagent and condition
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The reagent for Stage 1 is KCN or NaCN.
Condition: Aqueous conditions.
Step 4
Stage 2 reagent and condition
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The reagent for Stage 2 can be Ni or Pt or Pd.
Condition: Heating and reflux.
Step 5
Explain why 3-aminopentane is a stronger base than ammonia.
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3-Aminopentane is a stronger base than ammonia due to the presence of an alkyl group, which donates electron density to the nitrogen atom. This increases the availability of the lone pair on nitrogen for protonation, enhancing its basicity.
Step 6
Justify the statement that there are no chiral centres in 3-aminopentane.
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3-Aminopentane does not have any chiral centers because the nitrogen atom is not attached to four different groups. Therefore, it does not exhibit chirality.
