Summary OCR A LEVEL CHEMISTRY - ORGANIC FUNCTIONAL GROUPS TESTS

Organic
Functional Tests
Alkenes
 Add bromine water and shake Alcohols
 Positive result – bromine water Carboxylic acid
 Add dilute sulfuric acid and drops of
decolourises (orange to colourless)  Add sodium carbonate acidified potassium dichromate (VI)
Br  Positive result –  Water bath at 50˚C
Br2
efflorescence  Positive result –
CH3COOH + Na2CO3  CH3COONa + primary alcohol – orange to green
Br H2O + CO2 Secondary alcohol – remains orange
Tertiary alcohol can’t be oxidised
CH3CH2OH + [O]  CH3CHO + H2O

Haloalkane Carbonyls (aldehydes and ketones)
 Heat with NaOH + ethanol  Add Brady’s reagent
 Acidify with nitric acid then add AgNO3  Positive result – orange precipitate formed
 Positive result – AgX (X=halogen) precipitate
Aldehyde
formed
Ag+ + Br-  AgBr  Add tollens reagent and place the test-tubes in a water bath
(50˚C)
ion present observation  Positive result – silver mirror formed
Cl- white precipitate
Br- very pale cream precipitate CH3CH2CHO + [O]  CH3CH2COOH + Ag
I- very pale yellow precipitate
 Ketones will have no change to this test