4.6 Amines

Primary Amine

where nitrogen bonded to only one carbon atom

Secondary Amine

where nitrogen bonded to two carbon atoms

Tertiary Amine

where nitrogen bonded to three carbon atoms

What is an amine group

Reactants and conditions for the formation of primary amines from halogenoalkanes

halogenoalkane and ammonia dissolved in water/ethanol.

sealed tube to avoid escape of ammonia, which is used in excess

What kind of reaction is the formation of primary amines from halogenoalkanes

Nucleophilic Substitution

Mechanism for formation of primary amines from halogenoalkanes

Additional products of the formation of primary amines from halogenoalkanes

HBr

If excess halogenoalkane is added with ammonia dissolved in water/ethanol

Further substitution takes place and a secondary amine is formed

Describe the formation of primary amines from nitriles

produced by reduction of nitriles using LiAlH4

Describe the formation of aromatic amines from nitrobenzenes

Reducing agent = Iron in HCl or Hydrogen with a nickel catalyst

Reflux

Forms phenylamine

What allows amines to accept a proton

Amines, like ammonia, have a lone pair of electrons on the nitrogen atom.

What will shorter chain amines react with

water forming an equilibrium

Equilibrium lies well over to the left

What is a test for amines

Red litmus paper-- red to blue

How are alkylamines stronger bases than ammonia

the alkyl groups ‘push’ electrons more onto the nitrogen atom, making it more δ- when compared with ammonia’s nitrogen.

Why are longer alkylamines stronger bases

The longer the chain the more significant the effect of the push of electrons

Why are phenylamines a weaker base than ammonia and alkylamines

the lone pair of electrons on the nitrogen becomes part of the delocalised π-electron system of the benzene ring. This makes the nitrogen relatively less δ-.

All …. react with acid to make a salt

amines

Describe the ethanoylation of primary amines using ethanoyl Chloride

Amines can act as nucleophiles due to the nitrogen lone pair. They attack the δ+ carbon of the carbonyl group in an acid chloride

Reaction of phenylamine and ethanoyl chloride

How is nitrous acid made

reacting sodium nitrate(III) (sodium nitrite) with dilute HCl.

Why does nitrous acid have to be made in situ

instability

What does the reaction of nitrous acid with aromatic and aliphatic amines form at room temp

alcohol, water and N2 gas

What does the reaction of primary aromatic amines with nitric acid form at 10 degrees

benzenediazonium chloride

Why must there be excess nitric acid in the reaction

so that all the amine is converted.

Benzenediazonium chloride can couple with unused phenylamine

Why is the product not isolated

pure benzenediazonium is explosively unstable

How are diazonium compounds useful as intermediates in the synthesis of organic compounds

1) If aqueous benzenediazonium chloride is warmed above 10 degrees a phenol is formed

2) Iodobenzene is formed when aqueous benzenediazonium chloride is warmed with aqueous potassium iodide

How to identify Nitrogen gas

Put lit splint in and nothing happens

What does the reaction of benzenediazonium chloride with phenols and amines form

coloured compounds called azodydes