Edexcel Jun 2014 (IAL) Paper 5 Q22

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22 Ketoprofen is an analgesic used in the treatment of arthritis-related inflammatory pains. A synthesis of ketoprofen from benzenecarboxylic acid is shown below. CH3CH2Br AlBr3 stage 3 HO Cl stage 1 reagent A stage 2 reagent B AlCl3 benzenecarboxylic acid Br stage 4 reagent C heat stage 5 OH ketoprofen (a) Identify reagents A, B and C by name or formula. (3) ABC20 *P42979A02032*<br /> (b) Stage 3 is an electrophilic substitution. (i) Write an equation for the formation of the electrophile and explain the role of the AlBr3 in this process. (2)(ii) Complete the mechanism for the electrophilic substitution in stage 3. You need only show the benzene ring on the right of the structure. This is given below. (3) *P42979A02132* 21 Turn over<br /> (c) The first step of stage 5 of the synthesis is the addition of a carbon atom to the chain. One way of achieving this is to replace the bromine atom with a nitrile group in a nucleophilic substitution. (i) Suggest the name or formula of a reagent that could be used in this nucleophilic substitution. Suggest a suitable solvent in which to carry out the reaction. (2)(ii) The second step of stage 5 is the conversion of the nitrile into ketoprofen. State the reagent or reagents required. (1)22 *P42979A02232*<br /> (d) Benzenecarboxylic acid and ketoprofen have different infrared spectra. (i) In the diagram below, insert in the boxes the wavenumber ranges for the infrared absorptions due to C O groups in benzenecarboxylic acid and ketoprofen. HO OH benzenecarboxylic acid ketoprofen (ii) Explain how these absorptions can be used to distinguish between the two compounds. (3) (1)(Total for Question 22 = 15 marks) *P42979A02332* 23 Turn over<br />

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