Ethanol reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile - AQA - A-Level Chemistry - Question 4 - 2019 - Paper 3

The type of mixture formed by the two isomers is called a racemic mixture.

Ethanol has a chiral center at the carbon atom attached to the hydroxyl group and the hydrogen. This allows for two different configurations (R and S forms) as the cyanide ion can attack from either side, leading to the formation of two isomeric products.

The 3D structures of the two isomers are as follows:

1. (R)-2-Hydroxypropanenitrile:
   • The -OH group is oriented upwards on the chiral carbon.
   • The CN group is oriented downwards.
2. (S)-2-Hydroxypropanenitrile:
   • The -OH group is oriented downwards on the chiral carbon.
   • The CN group is oriented upwards.

The two isomers are mirror images of each other, which can be represented by proper 3D diagrams with wedges and dashed bonds for clarity.

The suitable reagent for the conversion of 2-hydroxypropanenitrile into acrylonitrile is concentrated sulfuric acid (H₂SO₄) at a temperature of approximately 170°C.

The section of the polymer polyacrylonitrile can be represented as follows:

[-C-N≡C-CH₂-]n

This represents three repeating units in polyacrylonitrile, where the polymer backbone consists of alternating carbon and nitrogen atoms.