Hydrolysis of Esters - Acid

• The reverse of the esterification reaction is called?hydrolysis
• Ester hydrolysis is a useful reaction for creating biodegradable plastics
• Esters can be?hydrolysed?to reform the carboxylic acid and alcohol or salts of carboxylic acids by using either?dilute?acid?(e.g. sulfuric acid) or?alkali?(e.g. sodium hydroxide) and?heat
• When an ester is?heated under reflux?with?acid?an equilibrium mixture is established, meaning that the hydrolysis reaction is not complete

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

Hydrolysis of Esters - Alkaline

• However,?heating?the ester?under reflux?with?dilute alkali?(e.g. sodium hydroxide) is an?irreversible?reaction as the ester is fully hydrolysed and the reaction goes to completion
• The carboxylic acid produced reacts with excess alkali to form a?carboxylate salt?and?alcohol
• The?sodium?carboxylate?salt requires further?acidification?to turn into a?carboxylic?acid
  • The sodium carboxylate (-COO-) ion needs to get protonated by an acid (such as HCl) to form the carboxylic acid (-COOH)

   

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

Table showing differences in hydrolysis of esters

Answer:

Answer 1:?Ethanoic acid and ethanol

CH3COOCH2CH3?+ H2O ? CH3COOH + CH3CH2OH

Answer 2:?Sodium propanoate and methanol

CH3CH2COOCH3?+ NaOH → CH3CH2COONa + CH3OH

Soaps

• Vegetable oils and animal fats can be hydrolysed in?alkaline?conditions with?aqueous sodium hydroxide?to form soaps
• The process is also called?saponification
• Soaps are?carboxylate salts?of long-chain carboxylic acids, known as fatty acids
• When triglycerides / fats are hydrolysed in hot alkaline conditions, the product is a mixture containing glycerol (propane-1,2,3-triol) and the salts of the fatty acids, soaps