O-LevelChemistryOrganic Chemistry5070/21 · May/June 2021 · Q910 Marks
The structure of propenyl ethanoate is shown. H O | H-C-C—O—C—C=C | H H H H | H
- (a)Use the structure to explain why propenyl ethanoate is unsaturated.[1]
- (b)Describe a chemical test to show that propenyl ethanoate is unsaturated. test observation[2]
- (c)Propenyl ethanoate is prepared by the reaction between a carboxylic acid and an alcohol, as shown. H O | H-C-C—O-H | H + H H H | H-O-C-C=C | H → H O | H-C-C—O—C—C=C | H H H H | H + H-O-H
- (c)(i)Name the carboxylic acid used.[1]
- (c)(ii)The reaction uses concentrated sulfuric acid as a catalyst. Describe how a catalyst speeds up a chemical reaction.[2]
- (d)In an experiment 11.6 g of the alcohol is reacted with an excess of the carboxylic acid. The experimental yield of propenyl ethanoate is 6.72 g. [The relative formula mass of propenyl ethanoate is 100.]
- (d)(i)Show that the maximum possible yield of propenyl ethanoate is 20.0g.[3]
- (d)(ii)Calculate the percentage yield of propenyl ethanoate in this experiment.[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.
- 9(a) It has a carbon-carbon double bond
- 9(b) (aqueous) bromine / Br2 (1)
- 9(b) orange to colourless / decolourised (1)
- 9(c)(i) ethanoic acid
- 9(c)(ii) lowers activation energy (1)
- 9(c)(ii) by having an alternative pathway / alternative mechanism (1)
- 9(d)(i) relative formula mass of alcohol is 58 (1)
- 9(d)(i) mol of alcohol = 0.2 OR 11.6/58 (1)
- 9(d)(i) mass of ester = 0.2 × Mr AND 0.2 × 100
- 9(d)(i) OR Mr × 11.6/58 AND 100 ×.6/58 (1)
- 9(d)(ii) 33.6 (%)
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