Edexcel Jun 2013 (R) Paper 2 Q22

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22 Ethane-1,2-diol, CH2OHCH2OH, is commonly used in antifreeze for cars to lower the freezing temperature of the water in the car radiator. It reacts in a similar way to ethanol but both of the alcohol groups can react. (a) Write an equation for the complete reaction between sodium and ethane-1,2-diol. State symbols are not required. (2) (2) (b) Ethane-1,2-diol is very quickly oxidized to ethanedioic acid, (COOH)2, even under the conditions shown below. Water Water Thermometer Condenser Distillate Round-bottomed flask Reaction mixture However, ethanol requires stronger oxidizing conditions to be converted into ethanoic acid. Explain how you would change the above apparatus to achieve this oxidation of ethanol.12 *P42983A01220*<br /> (c) Draw the skeletal formula of ethanedioic acid. (d) Explain why phosphorus(V) chloride, PCl5, would not be a suitable reagent to be used to distinguish between ethane-1,2-diol and ethanedioic acid. (1) (1)*P42983A01320* 13 Turn over<br /> (e) (i) Depending on the reaction conditions, ethanol can be oxidized to either an aldehyde or to carboxylic acid. Infrared spectroscopy is a suitable technique for determining whether the oxidation product obtained is an aldehyde or a carboxylic acid. Draw, on the spectrum below, any peak(s) that you would expect to see between 4000 and 1500 cm1 if the product was an aldehyde and not a carboxylic acid. DATA The IR absorption ranges associated with some organic functional groups are given below: OH stretching in alcohols (variable, broad) at 37503200 cm1 (2) OH stretching in carboxylic acids (weak) at C=O stretching in aldehydes (strong) at C=O stretching in ketones (strong) at 33002500 cm1 17401720 cm1 17001680 cm1 C=O stretching in carboxylic acids, alkyl (strong) at 17251700 cm1 CH stretching in aldehydes (weak) at and (weak) at 29002820 cm1 27752700 cm1 100 / e c n a t t i m s n a r t 50 0 4000 3000 2000 wavenumber / cm1 1500 1000 500 (ii) The infrared spectrum of the distillate from the reaction in (e)(i) included a peak at 37503200 cm-1. What substance is likely to have caused this? (1)14 *P42983A01420*<br /> (iii) Mass spectrometry can be used to identify the products of the oxidation of ethanol. Suggest the formula of a fragment that would show when ethanoic acid is produced and would not be present in either ethanol or ethanal. (1)(f) Treatment of 2-bromoethanol, CH2BrCH2OH, with aqueous sodium hydroxide would be one way to produce ethane-1,2-diol. (i) Complete a possible mechanism for this reaction in the space below. C Br c H HOH2C HO (ii) Classify the mechanism and type of reaction in (f)(i): (3) (2) MechanismType (g) Aqueous silver nitrate can be used to test for the presence of bromide ions. Write an ionic equation for the reaction. Include state symbols in your answer. Ionic Equation *(h) It can be difficult to distinguish between the colours of the silver halides. The use of solutions of ammonia can be very helpful. A silver halide dissolved in concentrated ammonia to form a colourless solution. Explain why this result does not prove conclusively that the silver halide was silver bromide and give a further test to confirm that the silver halide is silver bromide. (2) (2)(Total for Question 22 = 19 marks) TOTAL FOR SECTION B = 37 MARKS *P42983A01520* 15 Turn over<br />

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