20   8 This question is about isomerism in organic compounds. (a) How many structural isomers are there with the formula C5H12? (1) A 2 B 3 C 4 D 5 (b) Propene reacts with bromine to form 1,2‑dibromopropane as the only product. Draw the mechanism for the reaction between propene and bromine. Include curly arrows and any relevant lone pairs and dipoles. (3) Turn over 21   (c) When propene reacts with a mixture of bromine and sodium chloride, it forms 1,2‑dibromopropane, 1‑bromo‑2‑chloropropane and 2‑bromo‑1‑chloropropane but no 1,2‑dichloropropane. (i) Explain, by reference to your mechanism in (b), why no 1,2‑dichloropropane forms. 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(ii) Explain why far more 1‑bromo‑2‑chloropropane forms than 2‑bromo‑1‑chloropropane. 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Use only molecules A and B as examples. CHCl C(CH3)Br CH3CH(OH)COOH A B Include in your answer: • how the different types of isomerism arise • the naming of alkenes with the formula A • the properties of isomers with the formula B • diagrams of the different isomers. 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Turn over 23   .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 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(Total for Question 8 = 14 marks)