Nitriles and hydroxynitriles
| English | Chinese | Pinyin |
|---|---|---|
| nitrile | 腈 | jīng |
| hydroxynitrile | 羟基腈 | qiǎng jī jīng |
| nucleophilic substitution | 亲核取代 | qīn hé qǔ dài |
| nucleophilic addition | 亲核加成 | qīn hé jiā chéng |
| hydrolysis | 水解 | shuǐ jiě |
| reduction | 还原 | huán yuán |
Adding a carbon
- Cyanide can add a carbon to a chain in two ways.
- A nitrile 腈 has the –CN group; a hydroxynitrile 羟基腈 also has an –OH.
- Nitriles are a useful synthetic hub.
Nitrile synthesis route
Follow nitriles and hydroxynitriles as carbon-chain extension tools.
Nitriles contain the –C≡N functional group and can be reduced to amines.
They add one carbon to the chain.
Two ways to add cyanide
- Nitrile: heat a halogenoalkane with KCN in ethanol — a nucleophilic substitution 亲核取代 that adds one carbon:
$$\text{C}_2\text{H}_5\text{Br} + \text{KCN} \rightarrow \text{C}_2\text{H}_5\text{CN} + \text{KBr}$$
- Hydroxynitrile: add HCN (KCN catalyst) to an aldehyde/ketone — a nucleophilic addition 亲核加成 across the C=O.
KCN substitutes to a nitrile; HCN adds to a hydroxynitrile
Heating a halogenoalkane with KCN in ethanol makes a nitrile, which usefully:
The CN group adds a carbon (a nucleophilic substitution); HCN with a carbonyl gives a hydroxynitrile instead.
Adding HCN to an aldehyde or ketone gives a hydroxynitrile by:
CN⁻ adds across the carbonyl; the O⁻ then takes an H⁺ — nucleophilic addition.
Match each nitrile fact.
Each item links the term to its correct meaning.
What nitriles become
- hydrolysis 水解 (warm with dilute acid) turns –CN into –COOH → a carboxylic acid:
$$\text{CH}_3\text{CN} + 2\text{H}_2\text{O} + \text{HCl} \rightarrow \text{CH}_3\text{COOH} + \text{NH}_4\text{Cl}$$
- reduction 还原 (H₂ + catalyst) turns a nitrile into an amine.
Hydrolysing a nitrile with dilute acid turns –CN into:
Hydrolysis converts the nitrile group to a carboxylic acid (with an ammonium salt by-product).
Reducing a nitrile (with H₂ and a catalyst) gives:
Reduction of a nitrile gives an amine — a route to a longer-chain amine.
Building longer chains
- Reacting a halogenoalkane with cyanide adds a carbon as a nitrile.
- Reducing the nitrile gives an amine — a key way to lengthen a carbon chain.
You've got it
- KCN + halogenoalkane → a nitrile (nucleophilic substitution, adds a carbon)
- HCN + carbonyl → a hydroxynitrile (nucleophilic addition)
- a nitrile hydrolyses to a carboxylic acid, or reduces to an amine