CIE Jun 2016 v3 Paper 4 Q10

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PMT 15 10 (a) Ethanedioic acid, C2O4H2, occurs in many vegetables. The amount that occurs in spinach can be estimated as follows.40.0 g of spinach leaves are crushed and mixed with distilled water, using a mortar and pestle. The mixture is filtered, and the leaves are washed with a little more water. The combined filtrate and washings are made up to 100.0 cm3 with water. A 25.0 cm3 portion of the resulting solution is added to a conical flask, along with an excess of dilute sulfuric acid. The acidified solution is warmed, and then titrated with 0.0200 mol dm3 KMnO4. The equation for the reaction between ethanedioic acid and acidified manganate(VII) ions is shown. 2MnO4+ 6H+ + 5C2O4H22Mn2+ + 10CO2 + 8H2O In the titration, 15.20 cm3 of KMnO4 was required to reach the end-point. Calculate the percentage by mass of ethanedioic acid in the spinach leaves. percentage of ethanedioic acid =% [3]UCLES 2016 9701/43/M/J/16 [Turn over<br /> PMT 16 (b) Ethanedioic acid can be converted into ethanedioyl chloride: HO2CCO2HCl OCCOCl (i) State a suitable reagent for this reaction.[1] (ii) For the reactions of ethanedioyl chloride below, suggest the structures of compounds J and K and draw them in the boxes. CH3OH COCl COCl H2NCH2CH2NH2 J (C4H6O4) K (C4H6N2O2) [2] (c) When ethanedioyl chloride is reacted with silver ethanedioate, AgO2CCO2Ag, in ethoxyethane at 30 C, an oxide of carbon, L, is formed. The molecule of L has no overall dipole and has molecular formula C4O6. The carbon-13 NMR spectrum of a solution of L in ethoxyethane, CH3CH2OCH2CH3, is shown below. 150 100 50(ppm) (i) Use the Data Booklet to state in the boxes below thevalues for the peaks in the spectrum which are due to the carbon atoms in ethoxyethane. CH3 CH2 CH2 CH3values (ii) Explain what the rest of the carbon-13 NMR spectrum indicates about the structure of L.[1] [2]UCLES 2016 9701/43/M/J/16<br /> (d) When pure L is reacted with an excess of CH3OH, a mixture of three compounds is formed. 17 PMT L and CH3OHM and N and O (C3H4O4) (C4H6O4) (C4O6) (C2H2O4) M is formed as one of the products when either N or O is heated with aqueous acid. The table gives information of the peaks recorded in the carbon-13 NMR spectra of M, N and O. compound peaks recorded in carbon-13 NMR spectrum M N O1625316016253160 (i) Suggest the structures of M, N and O. M, (C2H2O4) N, (C3H4O4) (ii) Suggest a structure for L that fits all the data given in (c) and (d). O, (C4H6O4) [3] L, (C4O6)UCLES 2016 9701/43/M/J/16 [1] [Total: 13] [Turn over<br />

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