6.3.1. Qualitative analysis of organic functional groups

Question 1

ALKENE

What is the chemical test?
What is the observation?

Answer 1

• Add bromine water drop-wise

- Bromine water decolourises from orange to colourless

Question 2

HALOALKANE

What is the chemical test?
What is the observation?

Answer 2

• Add silver nitrate an ethanol. Warm to 50 degrees C in a water bath.
• various colours:
  CHLOROALKANE: white precipitate.
  BROMOALKANE: cream precipitate.
  IODOALKANE: yellow precipitate.

Question 3

CARBONYL

What is the chemical test?
What is the observation?

Answer 3

• Add 2,4-dinitrophenylhydrazine.

- Orange precipitate.

Question 4

ALDEHYDE

What is the chemical test?
What is the observation?

Answer 4

• Add Tollen’s reagent (ammoniacal silver nitrate) and warm.
• Silver mirror produced.

Question 5

PRIMARY/ SECONDARY ALCOHOL + ALDEHYDE

What is the chemical test?
What is the observation?

Answer 5

• Add acidified potassium dichromate (VI) and warm in a water bath.
• Colour change from orange to green.

Question 6

CARBOXYLIC ACID

What is the chemical test?
What is the observation?

Answer 6

• Add aqueous sodium carbonate.

- Effervescence.