Edexcel Jun 2017 Paper 5 Q22

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22 This question is about some naturally occurring amino acids, which have the formula RCH(NH2)COOH. (a) Amino acids can exist as zwitterions. What is meant by the term zwitterion? (1)A E R A S I H T N I E T I R W T O N O D (b) In the amino acid serine, the formula of the R group is CH2OH. The structure of serine varies with pH. Draw its structure at pH 1.0 and at pH 10.0. (2) A E R A S I H T N I E T I R W T O N O D Structure at pH 1.0 Structure at pH 10.0 A E R A S I H T N I E T I R W T O N O D *P48070A01928* 19 Turn over<br /> (c) In the amino acid alanine, the formula of the R group is CH3. Alanine can polymerize forming a condensation polymer. Draw a section of this polymer showing two repeat units, displaying the link between them. (2) (d) Compound A is the amino acid 2-aminoethanoic acid. It can be converted in three steps into a cyclic compound, E, called hydantoin. Reagent B + HCl(g) CH2NH2 COOH Compound A 2-aminoethanoic acid KNCO +Cl CH2NH3 COOC2H5 Compound C CH2NHCONH2 COOC2H5 Compound D + Compound F CH2 N H H Compound E Hydantoin (i) State a property shown by all naturally occurring amino acids except for 2-aminoethanoic acid. (1)20 *P48070A02028* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> (ii) Name the two types of reaction which are occurring when 2-aminoethanoic acid is converted into compound C. (2)(iii) Suggest the identity of the other organic product, compound F, which forms when compound D is converted into compound E. (1)A E R A S I H T N I E T I R W T O N O D (iv) When compound E reacts with hot dilute hydrochloric acid, 2-aminoethanoic acid is formed again, along with other products. Suggest the type of reaction which is occurring. (1) A E R A S I H T N I E T I R W T O N O D(v) Suggest the identity of the two products which also form in the reaction in (d)(iv). (2)(Total for Question 22 = 12 marks) TOTAL FOR SECTION B = 47 MARKS A E R A S I H T N I E T I R W T O N O D *P48070A02128* 21 Turn over<br />

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