Animes and Forming Aliphatic / Aromatic Amines

What are amines?

A compound which has a nitrogen atom directly bonded to a carbon atom of an alkyl or aryl group.

What is a primary amine?

A compound where the nitrogen atom is bonded to only one carbon atom of an alkyl / aryl group.

What is a secondary amine?

A compound where the nitrogen atom is bonded to only 2 carbon atoms.

What is a tertiary amine?

A compound where the nitrogen atom is bonded to 3 carbon atoms.

What is a quaternary amine?

A compound where the nitrogen atom is bonded to 4 alkyl / aryl groups.

The nitrogen is positively charged; this is often referred to as the “quaternary ammonium ion.”

What is an aromatic amine?

A compound where the nitrogen atom is directly bonded to a benzene ring.

What two methods can be used to form aliphatic amines?

• Reacting halogenoalkanes with excess ammonia.

• Reducing nitriles.

Give the name of the reaction of a halogenoalkane with excess ammonia to form an amine.

Nucleophilic substitution.

The ammonia (NH₃) acts as the nucleophile.

State the reagents and conditions needed to form amines by reacting halogenoalkanes with excess ammonia.

Reagents:

• Excess ammonia dissolved in ethanol

Conditions:

• Heated under reflux

Describe how amines are formed by reducing nitriles.

Amines can be formed by reduction of nitriles:

• A suitable reducing agent (LiAlH₄) dissolved in dry ether is used.

State the method used when forming aromatic amines (e.g. phenylamine).

Reduction of nitrobenzene.

Describe how nitrobenzene can be reduced to form phenylamine.

Reagents:

• Tin catalyst

• Concentrated hydrochloric acid (HCl)

• Sodium hydroxide (NaOH)

Conditions:

• Heated under reflux

Why is sodium hydroxide (NaOH) added when reducing nitrobenzene to form phenylamine?

• When a tin catalyst and concentrated HCl is added to nitrobenzene, C₆H₅NH₃⁺Cl^- forms.

• NaOH is added to decompose the salt into phenylamine together with a complicated mixture of tin compounds.

How is phenylamine separated when reducing nitrobenzene?

Fractional distillation / steam distillation