OCR A Jun 2014 Paper 2 Q2

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1-Bromobutane, CH3CH2CH2CH2Br, reacts with methoxide ions, CH3O, by nucleophilic substitution. (a) Suggest how the methoxide ion can act as a nucleophile.[1] (b) Using the curly arrow model, suggest the mechanism for this reaction. Show any relevant dipoles. (c) 1-Iodobutane also reacts with methoxide ions. Indicate, by placing a tick in one of the boxes, how the use of 1-iodobutane would affect the rate of reaction compared with that of 1-bromobutane. [3] 1-Iodobutane does not change the rate 1-Iodobutane increases the rate 1-Iodobutane decreases the rate Explain your answer.[1] (d) The ethanoate ion, CH3COO also acts as a nucleophile when reacting with 1-bromobutane in a substitution reaction. Draw the skeletal formula and give the name of the organic product formed in this reaction. skeletal formula name of product[2]OCR 2014<br />
 (e) 1-Bromobutane (Mr, 136.9) can be made from a reaction of butan-1-ol, C4H9OH, as shown in the equation below. C4H9OH + KBr + H2SO4 C4H9Br + KHSO4 + H2O (i) Calculate the atom economy for the formation of 1-bromobutane in this reaction. atom economy =% [1] (ii) Suggest a reactant, other than a different acid, that could be used to improve the atom economy of making 1-bromobutane by the same method.[1] (iii) A student prepares a sample of 1-bromobutane. 5.92 g of butan-1-ol are reacted with an excess of sulfuric acid and potassium bromide. After purification, 9.72 g of 1-bromobutane are collected. Calculate the percentage yield. Give your answer to three significant figures.OCR 2014 percentage yield =% [3] [Total: 12] Turn over<br />

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