CHEMICAL PROPERTIES AND USES OF ESTERS

Chemical properties

Hydrolysis of esters:

Alcohol and acid are produced from the hydrolysis of ester, this reaction reverse to ester formation, Hydrolysis may take place by the use of dilute mineral acids as a catalyst and is called acid hydrolysis, Dilute mineral acid (H⁺) is used to prevent the reversible reaction.

CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH

Hydrolysis of esters may also be carried out by heating with aqueous alkalies, to produce the alcohol and the salt of the acid, this is called alkaline-hydrolysis or saponification, (since soap is the sodium salt of high carboxylic acids), NaOH is added to react with the produced acid converting it to salt and prevent the reversible reaction.

CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH

C₆H₅COOC₂H₅ + NaOH → C₆H₅COONa + C₂H₅OH

Hydrolysis of esters is the reaction of the ester with water (in an acidic medium) to form acid and alcohol, saponification is the heating of ester with aqueous alkalis to produce the alcohol and the salt of the acid, Soap is the sodium salt of high fatty carboxylic acids.

The hydrolysis product of ester depends on the reaction medium because in acidic medium, acid and alcohol are formed while in alkali medium, salt of organic acid and alcohol are formed, Ammonolysis is the reaction of esters with ammonia to produce acid amide and the alcohol.

CH₃COOC₂H₅ + NH₃ → CH₃CONH₂ + C₂H₅OH

C₆H₅COOC₂H₅ + NH₃ → C₆H₅CONH₂ + C₂H₅OH

The esterification reaction is not a neutralization reaction as it is a reversible reaction “incomplete”, It needs a dehydrating agent, It is a slow reaction because it takes place between molecules, water is formed due to the combination of molecules, H from alcohol and OH from acid.

Acid + alcohol ↔ ester + H₂O

The neutralization reaction is irreversible reaction “complete”, It is a fast reaction because it takes place between ions, water is formed due to the combination of ions H⁺ from acid and OH⁻ from alkali.

Acid + base → salt + H₂O

Uses of esters