Esters

6 marks · Normal

Butanol and ethanoic acid are used together in a laboratory to produce an ester. Answer the following questions about this reaction and the practical steps involved.

(a)

Name the ester formed in this reaction.

[1 mark]

(b)

Draw the structural formula for the ester you named in part (a).

[2 marks]

(c)

State the name of the catalyst used during this esterification reaction.

[1 mark]

(d)

Describe one step you would take in the laboratory to make the smell of the ester easier to detect after the reaction is complete.

[2 marks]

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) butyl ethanoate

(b) CH3COO(CH2)3CH3 · must show Correctly joined ester linkage: COO, Alkyl chain matching butyl, Ethanoate portion with two carbons

(d) After the mixture has cooled, pour it into a beaker half-full of sodium carbonate solution to neutralise excess acid and allow the ester to float on top so its smell can be detected. · must show add sodium carbonate solution, layer of ester floats for easier detection of smell

Show mark scheme and worked solution

Marking points

A1 (a) · 1 mark · Correct name: butyl ethanoate

M1 (b) · 1 mark · Drawing shows correct structure of ester, with correct ester linkage (COO) between ethanoate and butyl groups. (follow-through)

A2 (b) · 1 mark · Full structural formula is correct and complete (all atoms shown, correct position for COO and carbon chains). (follow-through)

A3 (c) · 1 mark · Correct identification of catalyst: concentrated sulfuric acid.

M2 (d) · 1 mark · Describes addition of sodium carbonate or other valid method to separate/neutralise acid.

A4 (d) · 1 mark · States that ester forms a separate layer or becomes easier to smell. (follow-through)

Worked solution

a) The ester made is called butyl ethanoate.

b) The structural formula for butyl ethanoate can be shown as:

Alternatively, displayed:

c) The catalyst used is concentrated sulfuric acid.

d) To make the smell of the ester easier to detect, after cooling, pour the reaction mixture into a beaker half full of sodium carbonate solution. The ester floats on the surface, allowing its scent to be more easily detected.