Organic Analysis (OC6)

Question 1

How do we test for unsaturated hydrocarbons?

Answer 1

Add a few drops of bromine water and shake.

Question 2

When bromine water is added to unsaturated hydrocarbons, what happens?

Answer 2

The bromine water decolourises.

Question 3

How do we test for haloalkanes?

Answer 3

There are 3 primary methods.

We can either add warm, aqueous, sodium hydroxide.

Or, we can acidify the haloalkane with nitric acid (HNO3).

Or, we can add aqueous silver nitrate (AgNO3).

Question 4

When these tests are performed, what colour precipitate is formed when a chloroalkane is present?

Answer 4

White precipitate.

Question 5

And if a bromoalkane is present, what colour precipitate is formed?

Answer 5

Cream precipitate.

Question 6

And if a iodoalkane is present, what colour precipitate is formed?

Answer 6

Yellow precipitate.

Question 7

If we want to make sure the halide is correct, what do we do?

Answer 7

We add dilute ammonia.

Question 8

If the precipitate dissolves in the dilute ammonia, what is the halide?

Answer 8

It is a chloro- halide.

Question 9

If it doesn’t dissolve, and we add concentrated NH4 (ammonia), what is the halide?

Answer 9

It is a bromo- halide.

Question 10

If it still doesn’t dissolve. what is the halide?

Answer 10

It is a iodo-halide.