13108 13 Benzene was first isolated by Faraday in 1825. (a) Both benzene and propene will react with bromine but in different ways. (i) Write equations for the reactions of bromine with benzene and bromine with propene. benzene: propene: [2] (ii) Complete the table below. Reaction of bromine with benzene Reaction of bromine with propene Name of mechanism IUPAC name of product [4] (iii) Explain why the mechanisms for the reactions in (a)(ii) are different. [2] 13108 [Turn over (b) (4-bromophenyl)methanal can be formed by the sequence of reactions shown below. CH3 CH3 Br CH2Br Br CH2OH Br Br C O H Step 1 Step 2 Step 3 Step 4 Step 5 (i) Name the reagent and catalyst used in the formation of methylbenzene in Step 1. reagent: catalyst: [2] (ii) Methylbenzene reacts with bromine in Step 2 in the same way that benzene reacts with bromine. Including any appropriate equations, outline the mechanism for the catalysed reaction of methylbenzene and bromine in Step 2, using curly arrows. [5] 13108 (iii) Suggest the name for the reaction mechanism which occurs during Step 3 of the reaction sequence. [1] (iv) Name the reagent and the reaction conditions needed to carry out Step 5. reagent: conditions: [2] (v) The sample of (4-bromophenyl)methanal obtained contains an organic impurity. The relative molecular mass of the impurity was determined to be 201. Draw the structure of this organic impurity and state its IUPAC name. IUPAC name [2] 13108 [Turn over (c) (i) (4-bromophenyl)methanal reacts with 2,4-dinitrophenylhydrazine. Write an equation for this reaction. [2] (ii) State how the purified organic product formed from the reaction in c(i) could be used to confirm the identity of (4-bromophenyl)methanal. [2]