Nitriles and amines
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The teaching part (2 min) is free to watch. A free account opens the whole lecture: 2 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- A way to add a carbon
- Making nitriles
- Hydrolysis of nitriles
Read the transcript of the teaching part
Last time
Before we start: last time, in Carboxylic acids and esters, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
A way to add a carbon
Most reactions change a functional group but leave the carbon chain alone. Making a nitrile does something rare: it adds one carbon atom. And that nitrile can then become a carboxylic acid or an amine, which is why nitriles are such useful steps in building longer molecules.
Making nitriles
From a halogenoalkane: heat under reflux with potassium cyanide in ethanol. This is nucleophilic substitution, and the chain gains one carbon. From a carbonyl compound: HCN with a KCN catalyst gives a hydroxynitrile by nucleophilic addition. Butane to pentanenitrile in two steps: bromine and ultraviolet light to make a bromobutane, then potassium cyanide in ethanol. Methanol to ethanenitrile: first make bromomethane with HBr, then use potassium cyanide.
Hydrolysis of nitriles
Heat the nitrile under reflux with dilute acid, such as hydrochloric acid. The product is a carboxylic acid and an ammonium salt. For ethanenitrile: CH three CN plus HCl plus 2 H two O goes to CH three COOH plus NH four Cl. Another example: HOCH two CH two Cl with KCN gives HOCH two CH two CN, which is hydrolysed to HOCH two CH two COOH. Step 1 is substitution; step 2 is hydrolysis.
How often it comes up
The whole chapter: Nitrogen Compounds, Nitrogen Compounds.
Chapter 19: Nitrogen compounds
- Nitriles and amines 4 min
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