Ethanol reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile - AQA - A-Level Chemistry - Question 4 - 2019 - Paper 3
Question 4
Ethanol 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:Ethanol 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 ethanol.
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Answer
The mechanism for the reaction between potassium cyanide and ethanol is known as nucleophilic addition.
Step 2
State the name of this type of mixture.
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Answer
The type of mixture is known as a racemic mixture.
Step 3
Explain how the structure of ethanol leads to the formation of two isomers.
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Answer
Ethanol has a chiral center at the carbon atom that is bonded to the hydroxyl (–OH) group. When potassium cyanide attacks the carbon atom, it can approach from either side, leading to the formation of two different isomers. These isomers are enantiomers due to their non-superimposable mirror image relationship.
Step 4
Draw 3D representations of the two isomers to show the relationship between them.
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Answer
The 3D structures of the two isomers are as follows:
For (R)-2-hydroxypropanenitrile:
For (S)-2-hydroxypropanenitrile:
These diagrams illustrate the spatial arrangement of the atoms around the chiral center.
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 is sulfuric acid (H₂SO₄) under heating conditions, typically around 170 °C.
Step 6
Draw a section of the polymer polyacrylonitrile, showing three repeating units.
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Answer
The structure of polyacrylonitrile can be represented as follows:
-[C(CN)=C(CN)-]_n
This notation shows the repeating units of the polymer.
