Tests for functional groups

• Test for Aldehydes:

  Tollens Reagent: formed by mixing aqueous ammonia and silver nitrate

  Conditions: Heat gently

  With Aldehydes, forms a silver mirror coating inside the tube

  With Ketone, results in no change
• Tests for Aldehydes:

  Fehling's Solution- Contains blue copper 2+ions

  Conditions: Heat gently

  With Aldehydes Blue copper solution forms a red precipitate

  With Ketones no visible change
• Test for Carboxylic acid:

  Presence of -COOH can be tested by adding Sodium Carbonate, if positive it will fizz releasing CO2(effervescence)
• Test for Halogenoalkanes:

  Aqueous silver nitrate is added and if a halogenoalkane is present a precipitate is formed

  The faster the reaction, the faster the substitution the more reactive halogenoalkane- depends on reactivity of c-x bond

  
  

  Iodine = yellow precipitate Very reactive

  Bromine = Cream precipitate slightly reactive

  Chlorine = White precipitate Slow reaction
• Test with acyl chloride:

  Reaction with silver nitrate- leads to slow formation of HCl forming a white precipitate
• Test for Alkenes:

  
  

  Add Bromine water solution should go from orangey- brown to colourless in presence of a alkene
• Test with primary and secondary alcohols and aldehydes:

  
  

  Add Acidified Potassium Dichromate if Positive test solution should go from orange to green