Chemistry 9701 · AS & A Level · 6.1

6.1 — practice question

The structure of compound V is shown here. A sample of V is hydrolysed using an excess of hot aqueous alkali. A polypeptide made from four amino acids, A, B, C and D, is completely hydrolysed and then examined by gas-liquid chromatography.
(a)[2]

Describe how ethanoyl chloride and chlorobenzene differ in their reactivity with water. Explain your answer.

(b(i))[2]

Name all the functional groups in V.

(b(ii))[1]

Deduce the number of possible optical isomers for V.

(b(iii))[1]

Suggest one reason, apart from better biological activity and lower dosage required, why synthesising a single optical isomer of V is beneficial for use as a drug.

(c)[3]

A sample of V is hydrolysed with an excess of hot aqueous alkali. The products are separated from the reaction mixture at pH 12. Draw the structures of the two organic products formed by the complete alkaline hydrolysis of V in Fig. 8.1.

(d(i))[1]

A polypeptide made from four amino acids, A, B, C and D, is fully hydrolysed and then analysed by gas-liquid chromatography. The chromatogram obtained is shown in Fig. 8.2. The number above each peak gives the area under the peak, and that area is proportional to the mass of the amino acid in the mixture. Calculate the percentage by mass of amino acid A in the original mixture.

(d(ii))[1]

Amino acid D has the longest retention time. Explain why D has a longer retention time than the other amino acids A, B and C.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: chlorobenzene reacts less readily than ethanoyl chloride

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