Functional Group Tests

• Alkene

  • Reagent: Bromine Water
  • Result: Orange colour decolourises
• Carbonyl

  • Reagent: 2,4-DNP
  • Result: Forms orange ppt
• Aldehyde

  • Reagent: Tollens Reagent (AgNO3/NH3) and heat
  • Result: Forms Silver Mirror
• Carboxylic Acid

  • Reagent: Carbonate ions CO2^3 - e.g. Sodium carbonate
  • Result: Effervescence of CO2 evolved
• Primary and Secondary Alcohol and Aldehyde

  • Reagent: Sodium dichromate and sulphuric acid
  • Result: Orange to green colour change
• Haloalkane

  • Reagent: Warm with aqueous silver nitrate in ethanol
  • Result: Slow formation of white ppt
  • CHLOROalkane = white ppt of AgCl
  • BROMOalkane = cream ppt of AgBr
  • IODOalkane = yellow ppt of AgI
• Phenols

  • Test acidity by pH measurement/indicator then add Na2Co3 - no effervescence (too weak acid)
  • Reagent: Will react with sodium and sodium hydroxide- won’t react with Carbonate ions CO3
  • Result: Fizzing with sodium but no reaction with sodium carbonate
• Ketone

  1. Reagent: 2, 4 DNP
  2. Result: Forms orange ppt
  3. Reagent: Tollens reagent
  4. Result: No silver mirror