F324: Module 1: Organic Nitrogen

Question 1

I) What is the functional group of an amine?

Answer 1

NH2

Question 2

I) Comment on the solubility of primary amines in water.

Answer 2

Primary Aliphatic amines are generally soluble in water due to the fact that the NH2 group can form hydrogen bonds with the water molecules. As the number of carbon atoms in the chain increases, the solubility of the amine decreases.

Question 3

I) What does the Nitrogen’s lone pair of electrons allow primary amines act as bases?

Answer 3

It means that they are proton acceptors making them bronzed-lowry bases. They act as bases because primary amines react with acids to form salts.

Question 4

I) What would the product of this reaction be?

Ethylamine + Hydrochloric acid = ?

Answer 4

Ethylammonium chloride

Question 5

I) Why are primary amines weak alkalis?

Answer 5

In water, they lead to the formation of OH- ions making the weak alkalis.

Question 6

I) How would you prepare an aliphatic amine?

Answer 6

Excess ammonia is refluxed with a halogenoalkane (usually a bromoalkane) with ethanol as the solvent (ethanolic ammonia).

e.g. Ammonia + Bromoethane = Ethylamine + Ammonium Bromide
NH3 + CH3CH3Br = CH3CH2NH2 + HBr

The excess ammonia then reacts with the HBr to form ammonium bromide: NH4+Br-

Question 7

I) How would you prepare an aromatic amine?

Answer 7

You would reflux a nitro compound with a mixture of tin and concentrated HCl.

The general equation may be written as:
ArNO2 + 6[H] = ArNH2 + 2H2O

Question 8

I) Describe the first stage that you would need to perform in order to produce an azo-dye.

Answer 8

Sodium Nitrite (NaNO2) and Hydrochloric acid (HCl) react to form Nitrus acid (HNO2) and sodium chloride (NaCl).

Phenylamine + Nitrus acid = Benzenediazonium chloride + NaCl + water

The temperature should be below 10 degrees because the benzenediazonium chloride decomposes at higher temperatures.

Question 9

I) Describe the second stage that you would need to perform in order to produce an azo-dye (starting from benzenediazonium chloride).

Answer 9

The benzenediazonium chloride is added to phenol in the presence of NaOH. An azo-dye is then formed.

Question 10

I) What is the azo group?

Answer 10

-N=N-

Question 11

I) List some of the uses of azo-dyes.

Answer 11

Food colouring
Colouring for clothing
Indicators such as methyl orange