nitrogen

Question 1

Describe hydrogen bonding in amines

Answer 1

There is some between simple amines at room temperature, but weaker than in alcohols. There is none in tertiary amines as they have no hydrogens.

Question 2

Reaction of NH3 with haloalkanes

Answer 2

An excess of concentrated ammonia dissolved in ethanol, under pressure.
R-X + 2NH3 —> R-NH2 + NH4X
Nucleophilic substitution.
Not usually used as the amine can react further with the haloalkane to form n-ary amines and quat-salts. This is minimised by using an excess of NH3

Question 3

Reduction of nitrile compounds

Answer 3

1) Formation of a nitrile from a haloalkane: warm ethanol,
R-X + KCN —> R-CN + KX
2) Reduction of the nitrile to form an amine: LiAlH4 in ethoxyethane ([H]) or Ni catalyst with heat (H2).

Question 4

Preparation of aromatic amines

Answer 4

The reduction of nitro compounds using tin and HCl, then adding NaOH as the previous process creates the salt.
Water is released.

Question 5

Basicity of amines

Answer 5

Amines are weak bases as the lone pair on N can readily accept a proton. The higher the electron density, the better it will accept H+, so the stronger the base.
The more alkyl groups, the stronger the base as the induction effect pushes electron density towards the N.
In aromatic amines however, the N’s lone pair is partially delocalised, so electron density is reduced.

Question 6

Nucleophilic addition-elimination reactions

Answer 6

Amines react with acyl chlorides and acid anhydrides to replace an H on the N with the acyl group.
This produces an amide and a molecule of acid.
A second molecule of the amines reacts with the acid to form a salt.