3.5 - Testing for organic functional groups

Question 1

Test for alkene

Answer 1

Shake with bromine water

Colour change from orange to colourless

Addition reactions takes place

Question 2

Test for alcohol

Answer 2

Add Oxidising agent - potassium dichromate - to substance

Add stopper to test tube and shake well

Place in water bath

If 1o or 2o present, colour change from orange to green.

If 3o present, no change in colour

Question 3

Test for aldehyde - Fehlings solution

Answer 3

Felling solution -
Warm w aldehyde, so it becomes a caboxylic acid.

Colour change from clear blue to red predicate forming

Keaton’s cannot be oxidised so no change in colour

Question 4

Test for aldehyde - tollens reagent

Answer 4

Warm w aldehyde
Aldehyde oxidised to carboxylic acid
Ag ions are reduced to ag atomds
Produces a silver mirror

Keaton’s cannot be oxidised so this won’t form

Question 5

Test for carboxylic acid

Answer 5

Sodium carbonate
Produced effervescence