Esters

Esters

Sweet-smelling oily liquids used in food flavourings and perfumes

How are esters formed

When alcohols and carboxylic acids react in esterification reactions

What does the first part of an ester’s name come from

The alcohol—it indicates the length of its carbon chain and ends in -yl

What does the second part of an ester’s name come from

The carboxylic acid—it indicates the length of its carbon chain and ends in -oate

Ester formed when ethanol reacts with propanoic acid

Ethyl Propanoate

Ester formed when Butanol reacts with methanoic acid

Butyl Methanoate

Ester formed when Pentanol reacts with ethanoic acid

Pentyl Ethanoate

Method for preparing ethyl ethanoate

• Heat a mixture of ethanoic acid, ethanol, and concentrated sulfuric acid in a water bath or electric heater

• The ester then distilled as soon as it is formed and collected in a separate beaker by condensation

• As esters have low boiling points,they are the first to evaporate from the reaction mixture. Distillation prevents the reverse reaction from occuring.

How is the ester tested and purified after preparation

• The distillate can be smelt to check if an ester has been produced.

• Small amounts of ethanoic acid, sulfuric acid, and ethanol may also be present.

• To remove acidic impurities, sodium carbonate solution is added until fizzing stops (CO₂ release ends).

• Calcium chloride solution is added to remove ethanol