Edexcel Jan 2016 (IAL) Paper 5 Q22

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SECTION C Answer all the questions. Write your answers in the spaces provided. 22 Naphthalene is a white solid traditionally used in mothballs and is extracted from coal tar. It is an arene which can be represented by the formula below. Although it is an aromatic compound, naphthalene has carbon to carbon bonds of different lengths. Like benzene, naphthalene undergoes electrophilic substitution. Substitution usually occurs at one of the carbons 1, 4, 5 or 8 and naphthalene reacts under milder conditions than benzene. Oxidation of naphthalene, using oxygen gas with vanadium(V) oxide catalyst at about 650 K, produces phthalic anhydride: A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P46941A02128* 21 Turn over<br /> (a) State which physical method would be used to determine the lengths of the carbon to carbon bonds in naphthalene. (1)(b) Use your knowledge of benzene to draw an alternative way of representing the structure of naphthalene. Explain what this structure represents and how it arises. (3)22 *P46941A02228* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> (c) Naphthalene is nitrated using a mixture of concentrated nitric and sulfuric acids. Write a mechanism for this reaction. Include one or more equations to show how the electrophile is formed. (4) A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P46941A02328* 23 Turn over<br /> (d) 1.28 g of naphthalene is completely burned in oxygen. Write the equation for the combustion of naphthalene. State symbols are not required. Calculate the volume of carbon dioxide produced, measured at room temperature and pressure. 1 mol of a gas occupies 24.0 dm3 at room temperature and pressure. (e) Suggest the reagent and appropriate conditions for the synthesis of decalin from naphthalene. Decalin (3) (2)24 *P46941A02428* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> A E R A S I H T N I E T I R W T O N O D (f) When phenol is heated with phthalic anhydride in the presence of the catalyst concentrated sulfuric acid, the indicator phenolphthalein is formed. HO OH Phthalic anhydride Phenolphthalein (i) When phenol reacts with phthalic anhydride to form phenolphthalein, state the inorganic product of the reaction. (1)A E R A S I H T N I E T I R W T O N O D H3 In+ (ii) When phenolphthalein is colourless it can be represented as H2In. At very low pH, H3In+ is formed which is orange. Between pH 9 and 12, In2 is formed which has the familiar pink colour. By referring to the structure of phenolphthalein given above, suggest how these two ions are formed. (2)In2A E R A S I H T N I E T I R W T O N O D *P46941A02528* 25 Turn over<br /> (g) Coal tar also contains 2-naphthol. OH 2-naphthol and phenol react with phenylamine in a similar way to form dyes. Suggest a synthesis of a chemical dye starting with 2-naphthol and phenylamine. You should include chemicals and conditions for your reactions. Suggest the structural formula of your dye. D O N O T W R I T E I N T H I S A R E A (4) D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A (Total for Question 22 = 20 marks) TOTAL FOR SECTION C = 20 MARKS TOTAL FOR PAPER = 90 MARKS 26 *P46941A02628*<br />

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