12188 13 Petroselinic acid is a long chain fatty acid which is found in coriander seeds. CH3(CH2)10CH CH(CH2)4COOH petroselinic acid It is of interest because ozonolysis gives auric acid and adipic acid, used in the manufacture of nylon. CH3(CH2)10CH CH(CH2)4COOH →  CH3(CH2)10COOH  +  HOOC(CH2)4COOH petroselinic acid                      auric acid                adipic acid (a) Petroselinic acid is a positional isomer of oleic acid. It has the double bond in position 6; in oleic acid it is in position 9. (i) Suggest the meaning of the term positional isomer. [2] (ii) Draw the structures of the two fatty acids which are produced when oleic acid is ozonolysed. [2] O3 12188 [Turn over (b) The amount of petroselinic acid in coriander seeds can be determined by GLC. Petroselinic acid, which is a white solid, is first converted into its methyl ester which is a liquid. (i) Suggest why petroselinic acid is a solid and methyl petroselinate is a liquid. [2] (ii) Suggest why petroselinic acid is converted into the methyl ester for GLC analysis. [1] (iii) Explain how the percentage of petroselinic acid in a sample can be determined from a GLC chromatography trace. [2] 12188 (c) Nylon is made from the reaction of adipic acid with 1,6-diaminohexane. It is a condensation polymer. (i) Draw one repeating unit of the nylon polymer formed when adipic acid reacts with 1,6-diaminohexane. [2] (ii) Explain what is meant by the term condensation polymer. [1] (iii) Explain why nylon contains an amide bond and not a peptide link despite the fact that both bonds have the same structure. [1] (iv) Kevlar is a polymer formed by the reaction of 1,4-diaminobenzene with terephthaloyl dichloride. Write the equation for the reaction of one molecule of 1,4-diaminobenzene with one molecule of terephthaloyl dichloride. [3] 12188 [Turn over (v) Explain why both nylon and kevlar are biodegradable. [2] (d) Enzymes are also condensation polymers. Explain the primary, secondary and tertiary structures of enzymes. Include in your answer an explanation of the effect of pH and temperature on enzyme activity. In this question you will be assessed on using your written communication skills including the use of specialist scientific terms. [6]