g - Esters

4g (4.38-4.43)

Esters functional group

-COO

Esters are formed from…

an alcohol + carboxylic acid

in presence of acid catalyst (e.g. conc. sulfuric acid)

Ethyl ethanoate

Ester produced when ethanol + ethanoic acid react in presence of acid catalyst

Naming esters

Names end in ‘-oate’

First part of name - alcohol

Second part of name - acid

Esters are used…

in perfumes as many of them have pleasant smells + volatile (evaporate easily)

Also used to make food flavourings e.g. esters that taste of apple, orange etc.

Preparing sample of ester

How to make ethyl ethanoate:

• Add a few drops of conc. sulfuric acid to boiling tube using dropping pipette

• Add 10 drops of ethanoic acid

• Add equal volume of ethanol

• Place boiling tube in beaker of water + place on tripod

• Heat using Bunsen burner until water boils, then turn off Bunsen

• After 1 min, remove tube and allow to cool

• Once cool, pour mixture into test tube of sodium carbonate solution + mix
  Layer of ester should form on top of solution