Ethanal reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile - AQA - A-Level Chemistry - Question 4 - 2019 - Paper 3
Question 4
Ethanal reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile.
1. Name the mechanism for the reaction between potassium cyanide an... show full transcript
Worked Solution & Example Answer:Ethanal reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile - AQA - A-Level Chemistry - Question 4 - 2019 - Paper 3
Step 1
Name the mechanism for the reaction between potassium cyanide and ethanal.
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Answer
The mechanism for the reaction between potassium cyanide and ethanal is known as nucleophilic addition.
Step 2
State the name of this type of mixture.
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Answer
The name of this type of mixture is racemic mixture.
Step 3
Explain how the structure of ethanal leads to the formation of two isomers.
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Answer
The structure of ethanal has a carbonyl group (C=O) and is asymmetric, which allows for different spatial arrangements when a nucleophile attacks. This leads to the formation of two isomers due to equal chances of the nucleophile attacking from either side of the carbonyl carbon.
Step 4
Draw 3D representations of the two isomers to show the relationship between them.
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Answer
The 3D representations are as follows:
For (R)-2-hydroxypropanenitrile:
For (S)-2-hydroxypropanenitrile:
These structures demonstrate their relationship as stereoisomers.
Step 5
Suggest a suitable reagent and conditions for the conversion of 2-hydroxypropanenitrile into acrylonitrile.
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A suitable reagent for the conversion of 2-hydroxypropanenitrile into acrylonitrile is concentrated sulfuric acid (H₂SO₄) or phosphoric acid (H₃PO₄) at a heat of about 170°C.
Step 6
Draw a section of the polymer polyacrylonitrile, showing three repeating units.
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Answer
The structure of polyacrylonitrile with three repeating units can be represented as follows:
