Uses of esters
4 marks · NormalTable 1 shows the common smells of some esters.
| Ester | Smell |
|---|---|
| Methyl butanoate | Apple |
| Ethyl butanoate | Pineapple |
| Propyl ethanoate | Pear |
| Pentyl ethanoate | Banana |
State which ester would be suitable to add a pear flavour to a drink.
Give one reason why esters are used in food flavourings.
A manufacturer wants to create a banana-flavoured sweet. Name the ester they should use.
Suggest why perfumes often contain a mixture of esters.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Propyl ethanoate · must show Propyl ethanoate
(b) Esters provide fruity/sweet smells or flavours.
(c) Pentyl ethanoate · must show Pentyl ethanoate
(d) To make more interesting or complex scents.
Also accept: c: Allow amyl ethanoate for pentyl ethanoate
Common mistakes: wrong ester for correct fruit; mixing up food and perfume contexts
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States 'Propyl ethanoate' for pear flavour
B2 (b) · 1 mark · Reason—e.g. 'give fruity taste' or 'pleasant smell'
B3 (c) · 1 mark · States 'Pentyl ethanoate' (accept 'amyl ethanoate') for banana flavour
B4 (d) · 1 mark · Reason: e.g., 'to create more complex scents'
Worked solution
(a) Propyl ethanoate is suitable for a pear flavour.
(b) Esters are used because they have pleasant, fruity smells.
(c) Use pentyl ethanoate (or amyl ethanoate, the same compound).
(d) Using a mixture creates a more interesting scent.