A-LevelChemistryCarboxylic acids and derivatives9701/41 · Oct/Nov 2019 · Q811 Marks

Proteins are natural polymers. When one particular protein is partially hydrolysed the product mixture includes tripeptide E. tripeptide E HO H N. NH₃⁺ N H O HO

(a)(i)Describe the conditions that could be used to hydrolyse E to produce a mixture of three amino acids. [1][1]
(a)(ii)Draw the structures of the three amino acids produced by this hydrolysis reaction. The three amino acids should be shown in the correct form for the conditions you have chosen in (a)(i). [2][2]
(b)(i)type of force/bond: pair of groups responsible:[1]
(b)(ii)type of force/bond: pair of groups responsible:[1]
(b)(iii)type of force/bond: pair of groups responsible:[1]
(c)(i)Draw the structure of a compound that can polymerise to produce a polyamide, without the need for a second monomer. [1][1]
(c)(ii)Draw the structures of two different compounds that can polymerise together to produce a polyester with four carbon atoms per repeat unit. Name the two compounds. [4][4]

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 (Oct/Nov 2019). The mark or mark type is shown in brackets.

[1] any one from: • OH-/ NaOH; aqueous / dilute; heat under reflux • H+ / HCl / H2SO4, aqueous / dilute; heat under reflux • protease or named protease; water; T = 30°-40°C
[2] M1: three amino acids in any ionic / non-ionic states [1] M2: three amino acids in the correct ionic state for their conditions [1]
[1] • permanent dipole-dipole one group that will have a δ⁺ and another with δ⁻ e.g. CO, NH, COOH, OH BOTH [1]
[1] • hydrogen bonds one group that will have a Hδ⁺, e.g. NH, OH and another with lone pair, e.g. NH, COOH, OH, CONH2 BOTH [1]
[1] • ionic bonding NH3+ and COO- BOTH [1] ALLOW • London forces • C4H9 groups or parts of these alkyl groups
[1] any structure containing one COOH / COCl and NH2 groups in the same molecule
[4] HOCH2CH2OH [1] ethan(e)-1,2-diol [1] ecf for diols HO2CCO2H or CIOCCOCI [1] ethan(e)dioic acid or ethan(e)dioyl chloride [1] ecf for diacids / diacyl chlorides

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