Edexcel Jun 2010 Paper 5 Q22

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PMT 22 Paracetamol is possibly the most widely used analgesic (painkiller) in the world. It can be made from phenol as shown below. OH OH OH Step 1 Step 2 NO2 NH2 Step 3 OH NHCOCH3 Paracetamol (a) The nitration of phenol in step 1 uses dilute nitric acid at room temperature, whereas the nitration of benzene requires a mixture of concentrated nitric and sulfuric acids at about 55C. (i) Give the mechanism for the nitration of benzene, including the equation for the reaction that produces the electrophile. (4) 14 *N36507A01428*<br /> PMT *(ii) Explain why phenol can be nitrated under much milder conditions than those required to nitrate benzene. (2)(iii) Suggest reagents that could be used for step 2. (2)(iv) Suggest the name or formula of a reagent that could be used in step 3. (1)*(b) In the nitration of phenol, step 1, two compounds are produced. OH NO2 OH NO2 2-nitrophenol 4-nitrophenol These compounds can be separated by steam distillation, since 2-nitrophenol is volatile in steam but 4-nitrophenol is not. Describe briefly the technique of steam distillation and give ONE advantage of steam distillation over normal distillation. (3)*N36507A01528* 15 Turn over<br /> PMT (c) The nmr spectrum of paracetamol is given below. The peaks at 6.7 and 7.4 ppm are due to the protons on the benzene ring and are both doublets. Explain why these two peaks are doublets but all the other peaks are singlets. [There is no need to refer to your data booklet] (2) OH NHCOCH3 Paracetamol 11 10 5 6/ ppm(Total for Question 22 = 14 marks) 16 *N36507A01628*<br />

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