Esters
7 marks · HardSome esters have pleasant smells and are widely used in everyday products.
Give the systematic name of the ester with molecular formula C3H7COOCH3.
State the names of the alcohol and the carboxylic acid needed to make this ester.
Suggest one use of this ester and explain why esters are suitable for this use.
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) methyl butanoate · must show Accept: methyl butanoate; do not accept butyl methanoate
(b) methanol and butanoic acid · must show Methanol, Butanoic acid
(c) food flavouring because esters have pleasant, fruity smells and are volatile · must show Use: flavouring or perfume, Explanation: esters are volatile and have pleasant smells
Also accept: Food flavouring; Perfume
Common mistakes: Swapping the positions of alcohol and acid; Incorrect systematic name (e.g., butyl methanoate instead of methyl butanoate)
Show mark scheme and worked solution
Marking points
A1 (a) · 2 marks · Gives the correct systematic name: methyl butanoate (1 mark for 'methyl', 1 mark for 'butanoate')
B1 (b) · 2 marks · Correctly identifies both required reactants: methanol (1), butanoic acid (1)
C1 (c) · 1 mark · Gives a suitable use: food flavouring, perfume, or fragrance
C2 (c) · 1 mark · States esters are volatile
C3 (c) · 1 mark · States esters have pleasant or fruity smells
Worked solution
a. The systematic name for C3H7COOCH3 is methyl butanoate. The methyl group (from methanol) is attached to the oxygen, with the butanoate from butanoic acid.
b. The reactants are methanol (alcohol) and butanoic acid (carboxylic acid).
c. Use: Methyl butanoate can be used as a flavouring (or perfume). Esters are suitable for this use because they are volatile (evaporate easily) and have pleasant, fruity smells.