Tests for organic functional groups

Question 1

Test for alkenes

Answer 1

Bromine water- will go from brown to colorless (decolorizes)

Question 2

Test for haloalkanes

Answer 2

add aq NaOH and heat.
add dil NH3 (gets rid of carbonates and hydroxides)
add AgNO3.
AgCl-White ppt (dissolves in dil NH3)
AgBr-Cream ppt (dissolves in conc NH3)
AgI-Yellow ppt (doesn't dissolve)

Question 3

Aldehydes

Answer 3

Add Tohlen’s reagent (Ag)
Silver mirror formed.
Add Fehling’s reagent (Cu)
Brick-red ppt forms.

Question 4

Carboxylic acids

Answer 4

Add NaHCO3- turns limewater milky and effervescence is seen.

Question 5

Acyl chlorides

Answer 5

Add water to the sample slowly, misty white fumes given off.

Question 6

Amines

Answer 6

Basic- so just add universal indicator if blue/purple amine is present (fishy smell also)

Question 7

Alcohols

Answer 7

Add ethanoic acid with sulphuric acid (Catalyst) and heat to form an ester, this will have a sweet and fruity smell.

Question 8

Primary/Secondary/Tertiary alcohols

Answer 8

Add potassium dichromate acidified with dil H2SO4, warm gently.
if Primary/Secondary mixture goes from orange to green. if Tertiary then NVC.
To distinguish between primary and secondary if gone green take green solution then do either Fehling’s or Tohlen’s test.

Question 9

Aromatic compounds

Answer 9

Conc HNO3 and H2SO4 this forms fuming.