reactions

• combustion of alcohols:

  • produce carbon dioxide and water
  • reaction is exothermic
• oxidation of alcohols:

  • primary and secondary alcohols
  • potassium dichromate (VI), K2Cr2O7 acidified with dilute sulfuric acid, H2SO4
• If alcohol is oxidised the orange solution containing dichromate (VI) ions is reduced to a green solution containing dichromate (III) ions
• Primary alcohols oxidise to aldehydes or carboxylic acids
• Primary alcohols to aldehydes:

  • gentle heating with acidified potassium dichromate (Kr2Cr2O7 / H2SO4)
  • distillation
  • products: aldehyde (-anal / C=O) and water
• Primary alcohols to carboxylic acids:

  • heated strongly under reflux with an excess of acidified potassium dichromate (Kr2Cr2O7 / H2SO4)
  • products: carboxylic acid (-COOH) and water
• Oxidation of secondary alcohols:

  • heated under reflux with acidified potassium dichromate
  • colour change: orange to green
  • products: ketones + water
• tertiary alcohols do not undergo oxidation reactions
• dehydration of alcohols

  • water molecule removed
  • heated under reflux in the presence of an acid catalyst like conc. sulfuric or phosphoric acid
  • products: alkene + water
  • this is an elimination reaction
• substitution reactions of alcohols:

  • react with hydrogen halides to make haloalkanes
  • alcohol is heated under reflux with sulfuric acid and a sodium halide (which together form HBr)
  • products: haloalkane + water