Distinguishing between different organic compounds

Question 1

test for alkenes

Answer 1

Alkenes decolorize bromine water because they undergo an electrophilic addition reaction with bromine:

Question 2

test for aldehydes

Answer 2

Add Tollen’s reagent to the sample and heat. A silver mirror indicates the presence of an aldehyde.

Question 3

test for carboxylic acids

Answer 3

Add sodium carbonate solution to the sample. If effervescence is seen, and the gas produced turns limewater milky, a carboxylic acid is present.

Question 4

test for amines

Answer 4

Amines are basic.

Add universal indicator to the sample. If it turns blue/purple an amine is present. It will also have a fishy smell.

Question 5

test for alcohols

Answer 5

Alcohols react with carboxylic acids in the presence of sulphuric acid to make esters.

Add ethanoic acid to the sample, followed by sulphuric acid and heat. If a the mixture starts smelling sweet and fruity an alcohol was present.

Question 6

distinguishing tests for primary, secondary and tertiary alcohols

Answer 6

Primary alcohols can be oxidized to form aldehydes. Secondary alcohols are oxidized to form ketones. Tertiary alcohols cannot be oxidized.
Add potassium dichromate and dilute sulphuric acid to the mixture and warm gently.