OCR A Jun 2014 Paper 4 Q3

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12 3 Alanine, serine and proline are -amino acids. H2NCH(CH3)COOH H2NCH(CH2OH)COOH alanine serine COOH N H proline (a) (i) Alanine and serine react together to form two different dipeptides. Draw the structures of the two dipeptides that can form when alanine and serine react together. [2] (ii) The isoelectric points of alanine and serine are shown below. alanine, pH = 6.0 serine, pH = 5.6 Draw the structures of the ions formed at the following pH values. structure of alanine ion at pH 6.0 structure of serine ion at pH 10.0OCR 2014 [2]<br />
 (iii) Proline can polymerise to form poly(proline). Draw the structure of the repeat unit in poly(proline). 13 (b) A solution of serine was shaken with a few drops of D2O. The solution was then analysed using 1H NMR spectroscopy. Complete the table to predict the 1H NMR spectrum of serine after the addition of D2O. [1] 1H NMR spectrum for serine Chemical shift,/ ppm Relative peak area Splitting pattern [2]OCR 2014 Turn over<br />
 (c) Enalapril is a drug used in the treatment of high blood pressure. 14 N H enalapril COOH (i) On the structure above, mark each chiral centre with an asterisk (*). [1] (ii) Suggest two benefits of using single stereoisomers in the synthesis of drugs such as enalapril.[2]OCR 2014<br />
 (iii) Enalapril is broken down in the body by acid hydrolysis. 15 N H enalapril COOH Draw the structures of the three organic products of the acid hydrolysis of enalapril. [4] (iv) A scientist hydrolysed enalapril in the laboratory. The scientist then analysed the mixture of products using GCMS. Explain how GCMS enables the products to be identified.[1] [Total: 15]OCR 2014 Turn over<br />

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