Esters · Grade 12
In Grade 12 you get fluent with: esters: the –COO– group and their uses; making and naming esters.
Esters are made when an alcohol reacts with a carboxylic acid, with a little concentrated sulfuric acid as a catalyst; water is made too. They have the –COO– group, and they are volatile with fruity smells, so they are used in perfumes and flavourings. An ester is named from its alcohol first and its acid second: ethanol and ethanoic acid make ethyl ethanoate.
Key facts
- Alcohol + carboxylic acid ⇌ ester + water, with concentrated sulfuric acid as a catalyst. Ethanol + ethanoic acid → ethyl ethanoate.
- Esters are volatile with fruity smells: they are used in perfumes and flavourings.
- An ester is named from its alcohol first (ethyl) and its acid second (ethanoate).
Worked examples
Example 1
What is the functional group of the esters?
Answer: –COO–
Example 2
Which ester is made when ethanol reacts with ethanoic acid?
Answer: ethyl ethanoate
Example 3
Name the ester made from methanol and propanoic acid.
Answer: methyl propanoate
Example 4
Which catalyst is used when an alcohol reacts with a carboxylic acid to make an ester?
Answer: concentrated sulfuric acid
Example 5
What are esters used for?
Answer: perfumes and food flavourings