This question is about amines - AQA - A-Level Chemistry - Question 10 - 2018 - Paper 2
Question 10
This question is about amines.
The infrared spectra A, B and C are those of a primary amine, a tertiary amine and a nitrile, but not necessarily in that order.
A
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Worked Solution & Example Answer:This question is about amines - AQA - A-Level Chemistry - Question 10 - 2018 - Paper 2
Step 1
Give the letter of each compound in the correct box.
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Answer
A: primary amine
B: tertiary amine
C: nitrile
Step 2
Draw the skeletal formulas of these three secondary amines.
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Answer
CH₃-CH₂-CH(NH₂)-CH₃
CH₃-CH(NH₂)-CH₂-CH₂-CH₃
(CH₃)₂CH-NH-CH₂-CH₃
Step 3
Justify the statement that it is better to prepare primary amines from nitrites rather than from halogenoalkanes.
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Answer
Using nitrites leads to a higher atom economy as it minimizes the production of side products, whereas halogenoalkanes may yield a mixture of products due to their reactivity.
Step 4
Draw the structure of a primary amine with four carbon atoms that cannot be formed from a nitrile.
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The structure can be depicted as CH₃(CH₂)₂CH₂NH₂.
Step 5
Give an equation for the reaction that occurs.
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C₃H₇NH₂ + H₂O → C₃H₇NH₃^+ + OH⁻
Step 6
Describe what is observed when Universal Indicator is added to this solution.
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The solution turns purple, indicating a basic pH.
Step 7
Give an equation for the reduction of nitrobenzene to form phenylamine.
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Answer
C₆H₅NO₂ + 6[H] → C₆H₅NH₂ + 2H₂O
Step 8
Explain why an aqueous solution is obtained in this reduction even though phenylamine is insoluble in water.
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Answer
The presence of hydrochloric acid during the reduction allows phenylamine to form an ionic salt, which is soluble in water, leading to an aqueous solution.
