Qualitative analysis of organic functional groups

• reactions can be carried out on a test-tube sale to identify the functional groups present in an organic compound
• alkane:

  • add bromine water dropwise
  • bromine water discoloured from orange to colourless
• haloalkane:

  • add silver nitrate and ethanol and warm to 50 degrees in a water bath
  • chloroalkane - white ppt
  • bromoalkane - cream ppt
  • iodoalkane - yellow ppt
• carbonyl:

  • add 2,4-dinitrophenylhydrazine
  • orange ppt
• aldehyde:

  • add Tollens' reagent and warm
  • silver mirror
• primary and secondary alcohol and aldehyde:

  • add acidified potassium dichromate (VI) and warm in a water bath
  • colour change from orange to green
• carboxylic acid:

  • add aqueous sodium carbonate
  • effervescence
• Phenol:

  • acidic compounds which can be tested using pH indicator paper
  • not as acidic as carboxylic acids and do not react with sodium carbonate
  • phenol undergoes electrophilic sub reaction with brome at RT
  • when bromine is added to an aqueous solution of phenol the bromine is decoloursed and a white ppt is formed