Compounds containing Nitrogen

Question 1

Hydrolysis of nitriles/amides

Product, R+C

Answer 1

= Carboxylic acid

> Dilute sulphuric acid

Question 2

Production of aliphatic amines

Mechanism, R+C, by-product

Answer 2

*Nucleophilic substitution
> Halogenoalkane
> Excess ammonia
> Ethanol solvent
= Ammonium salt (NH4X)

Question 3

Dehydration of an amide

Product, R+C

Answer 3

= Nitrile (-H2O)

> Phosphorus (V) oxide (P4O10)

Question 4

How would you make an aromatic amine?

R+C

Answer 4

> Nitrobenzene
> Steam distillation
> Concentrated HCl
> Granulated tin
> Aqueous sodium hydroxide (to neutralise phenylammonium ions)

Question 5

Explain the basicity of amines.

Answer 5

The nitrogen atom has a lone pair of electrons, these can act as a base by forming a co-ordinate bond with a hydrogen ion.

Question 6

Are amines soluble in water?

Answer 6

Only smaller amines are soluble in water due to hydrogen bonding.

Amines with longer hydrocarbon chains are insoluble in water because the chains force their way between the water and amine and break the hydrogen bond.

Question 7

Describe the boiling points of amines

Answer 7

BP increases with molecular mass, due to increased Van der Waals’ and is increased further by hydrogen bonding

Question 8

Ethanoylation of primary amines

Mechanism, products

Answer 8

*Nucleophilic addition-elimination
= N-substituted amide + HCl
The amide may react with the HCl produced to give an alkylammonium chloride

Question 9

Aliphatic amine + nitrous acid ->

Observation, R+C

Answer 9

Aiphatic alcohol + Nitrogen(g) + Water
~ The nitrogen gas is seen as colourless bubbles in the reaction mixture
> Room temp.

Question 10

Aromatic amine + nitrous acid –>

Below 5°C

Answer 10

Diazonium salt + Water

Question 11

Aromatic amine + nitrous acid –>
Above 10°C
(Observations)

Answer 11

Phenol + water + N2(g)

~ Black oily product and colourless bubbles of nitrogen gas

Question 12

Coupling reaction of a diazonium salt
Below 5°C
(Product, R+C)

Answer 12

= Azodye (contains -N=N- chromophore)

> Alkaline solution (aqueous NaOH)

Question 13

What happens if the diazonium salt is placed in water at room temperature?

Answer 13

Decomposition occurs producing

phenol + N2(g) + HCl

Question 14

Explain the high melting temperatures of amino acids

Answer 14

They can form zwitterions which are ionic, the strong attractive forces between positive and negative charges requires significantly more energy to overcome.

Question 15

How many possible dipeptides can be formed if two amino acids are joined together? What type of reaction is occuring?

Answer 15

If the two amino acids are the same then only one dipeptide may be formed. However, if the two amino acids are different then two different dipeptides may be formed.
Condensation reaction

Question 16

Hydrolysis of poly/dipeptides

Product, R+C

Answer 16

= Constituent amino acids
> 6M HCl
> Reflux/ Strong heat
> Neutralisation using alkali

Question 17

Describe 1° protein structure

Answer 17

The sequence of amino acids in a chain

Question 18

Describe 2° protein structure

Answer 18

The amino acid chains coil into pleated sheet or helix due to hydrogen bonding

Question 19

Describe 3° protein structure

Answer 19

The resulting overall 3D shape produced by electrostatic attraction and disulphide bridges

Question 20

Name 3 uses of proteins in living systems

Answer 20

1. Hair/feathers
2. Cartilage
3. Enzymes
4. Hormones
5. Source of energy
6. Transport

Question 21

List two features of addition polymerisation and give an example

Answer 21

1. Monomer needs to have a C=C double bond
2. No by-product
3. Only one starting material
   Example : polymerisation of propene to polypropene

Question 22

Give the reagents and conditions required for the polymerisation of an alkene

Answer 22

> Increased pressures, particularly with gaseous alkene molecules
A radical initiator (starts the reaction and is used up during the process)

Question 23

List two factors of condensation polymerisation and give the reagents required for the formation of a polyester

Answer 23

1. Two molecules join together with the elimination of a small molecule
2. The two starting materials need to be bi-functional
   Example : Ethane-1,2-diol + benzene-1,4-dicarboxylic acid –> PET

Question 24

What are the two starting materials required for the formation of Nylon-6,6?

Answer 24

1,6-diaminohexane and hexane-1,6-dioic acid

Question 25

What are the two starting materials required for the formation of kevlar?

Answer 25

Benzene 1,4-dicarboxylic acid and 1,4-diaminobenzene