Edexcel Jun 2017 (IAL) Paper 6 Q4

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4 The preparation of 1-methyl-2-nitrobenzene (2-nitrotoluene) is similar to the preparation of nitrobenzene. The following sequence gives the procedure in outline. Step 1 Step 2 Step 3 Step 4 A nitrating mixture is prepared by mixing 12.5 cm3 of concentrated sulfuric acid with 10.6 cm3 of concentrated nitric acid. Both acids are pre-cooled and the mixing is carried out very slowly. 9.20 g of methylbenzene is placed in a round bottom flask and the nitrating mixture is added very slowly while cooling the mixture. When mixing is complete, the mixture is allowed to warm to room temperature and then stirred for two hours. The reaction mixture is poured into water. The organic layer is separated and sodium hydrogencarbonate solution is added. The organic layer is separated again, and a drying agent is added before the mixture is distilled. Some of the physical properties of 1-methyl-2-nitrobenzene and the other significant organic products of this sequence are shown in the table. Name Structure 1-methyl-2- nitrobenzene 1-methyl-4- nitrobenzene 1-methyl-2,4- dinitrobenzene CH3 NO2 CH3 NO2 CH3 NO2 NO2 Melting Boiling temperature temperature / C / C 10.4 222 51.6 238 70 300 (decomposes) 12 *P48386A01216*<br /> (a) Complete the table of hazard symbols for nitric acid. Corrosive Toxic (b) Explain why in Step 1 the components of the nitrating mixture are pre-cooled and mixed very slowly. (1) (1)(c) Explain why Step 2 is carried out so that the reaction mixture is always at or below room temperature. (1)(d) State why sodium hydrogencarbonate solution is added in Step 3. (1)*P48386A01316* 13 Turn over<br /> (e) Suggest the temperature range at which 1-methyl-2-nitrobenzene would be collected in the distillation. (1)(f) Suggest the best way to obtain some pure 1-methyl-2,4-dinitrobenzene after the distillation. (1)(Total for Question 4 = 6 marks) TOTAL FOR PAPER = 50 MARKS 14 *P48386A01416*<br />

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