CIE AS Chemistry (9701) 2019-2021

Revision Notes

3.6.2 Esters

Hydrolysis of Esters

  • Esters can be hydrolysed to reform the carboxylic acid and alcohol by either dilute acid or dilute alkali and heat
  • When an ester is heated under reflux with dilute acid (eg. sulfuric acid) an equilibrium mixture is established as the reaction is reversible

 

Ester hydrolysis by dilute acid is a reversible reaction forming carboxylic acid and alcohol

  • However, when heated under reflux with dilute alkali (eg. sodium hydroxide) is an irreversible reaction and the ester is fully hydrolysed
  • This results in the formation of a sodium carboxylate salt which needs further acidification to turn into a carboxylic acid

 

Ester hydrolysis by dilute alkali is an irreversible reaction forming a sodium carboxylate salt and alcohol

Commercial Uses of Esters

  • Esters have sweet and fruity smells
  • They are therefore commercially used in perfumes and flavourings
  • The smaller esters such as ethyl acetate are furthermore used as solvents in organic chemistry as it can dissolve in a wide range of organic compounds
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