The amino acid serine, HOCH₂CH(NH₂)COOH, exists in two optically active forms. These optical isomers, isomer P and isomer Q, are shown in Fig. 8.1. [Figure 8.1 showing structures of Isomer P and Isomer Q] proline [Proline skeletal formula] glutamic acid [Glutamic acid skeletal formula]

1. (a)Isomer P and isomer Q have identical physical and chemical properties, with the exception of two specific properties. One of these two properties is their differing effect on plane polarised light. State the other property by which they differ.[1]
2. (b)A solution of pure isomer P of a particular concentration rotates plane polarised light by 5.0° in a clockwise direction. Describe how a solution of pure isomer Q of the same concentration affects plane polarised light.[1]
3. (c)State another term, in addition to stereoisomers, optical isomers and non-superimposable mirror images, which can be used to describe this pair of chiral compounds, isomer P and isomer Q.[1]
4. (d)Give the term used to describe a mixture containing equal amounts of isomer P and isomer Q.[1]
5. (e)Describe one way in which a single pure optical isomer of serine can be produced, instead of making a mixture of isomer P and isomer Q.[1]
6. (f)Complete Table 8.1 to describe the peaks seen in the proton (¹H) NMR spectrum of HOCH₂CH(NH₂)COOH dissolved in D₂O. Use as many rows in Table 8.1 as you need to, leaving the other rows blank. Table 8.1 group responsible for peak name of splitting pattern shown by peak explanation for splitting pattern[3]
7. (g)Proline is a naturally occurring amino acid. The skeletal formula of proline is shown. [Proline skeletal formula] State the number of peaks in the carbon-13 (¹³C) NMR spectrum of proline.[1]
8. (h)Glutamic acid is a naturally occurring amino acid. The skeletal formula of glutamic acid is shown. [Glutamic acid skeletal formula] The isoelectric point of glutamic acid is pH 3. A sample of glutamic acid is dissolved in a solution of pH 1. A strong alkali is then added until the pH of the mixture reaches pH 14. During this process all possible ionised forms of glutamic acid are present at different times, depending on the pH of the solution. Complete the boxes below to show four different ionised forms of glutamic acid that are present at the stated pH values. at pH 1 at pH3 at pH9 at pH 14[3]

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