22 7 This question is about the synthesis of organic compounds. (a) A student suggested the following plan for the synthesis of pentanoic acid from but-2-en-1-ol. OH OH CN OH O Step 1 LiAlH4 in dry ether Step 3 heat under reflux with NaOH(aq) but-2-en-1-ol pentanoic acid butan-1-ol Step 2 KCN in aqueous ethanol (i) LiAlH4 is a source of hydride ions, H−. Give a possible reason why LiAlH4 cannot be used to reduce alkenes. (1) ..................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) Give a suitable reagent and condition for Step 1. (2) .................................................................................................................................................................................................................................................................................... (iii) Step 2 is incorrect because alcohols can only be converted to nitriles via an intermediate compound. Identify a suitable intermediate compound by name or formula. (1) .................................................................................................................................................................................................................................................................................... (iv) Step 3 involves the hydrolysis of a nitrile. Give the additional reagent that should be added after heating under reflux with aqueous sodium hydroxide, to produce pentanoic acid. (1) .................................................................................................................................................................................................................................................................................... 23 Turn over (b) Devise a four-step synthesis, involving the use of a Grignard reagent, to convert benzene into benzoyl chloride. O Cl C Include the reagents and conditions for each step in the synthesis and the structures of the intermediates. (7) (Total for Question 7 = 12 marks) 24 BLANK PAGE