OCR A Jun 2015 Paper 2 Q2

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2 Butan-2-ol can be prepared using two different methods. Method 1 H3C CH3 Method 2 Br H2O(g) OH H NaOH(aq) butan-2-ol (a) Comment on the atom economy of each method, giving your reasons.[2] (b) State the catalyst required for Method 1.[1] (c) Average bond enthalpies can be used to calculate enthalpy changes. (i) What is meant by the term average bond enthalpy?[2]OCR 2015<br />
 (ii) Calculate the enthalpy change of reaction, Hr, for preparing 1 mol of butan-2-ol by Method 1. Average bond enthalpies are given below. Bond Average bond enthalpy / kJ mol1 OH CH CC CO C=C 464 413 347 358 612 Hr =kJ mol1 [3] (d) A student uses Method 2 to prepare 3.552 g of butan-2-ol from 2-bromobutane. The percentage yield of butan-2-ol is 80.0%. Calculate the mass of 2-bromobutane that the student uses. Give your answer to three significant figures.OCR 2015 mass of 2-bromobutane =g [3] [Total: 11] Turn over<br />

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