OCR A Jan 2013 Paper 4 Q1

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Answer all the questions. 1 Pyruvic acid, shown below, is an organic compound that has a smell similar to ethanoic acid. It is extremely soluble in water. OH H3C pyruvic acid (a) Explain why pyruvic acid is soluble in water. Use a labelled diagram to support your answer.[2] (b) Pyruvic acid can be prepared in the laboratory by reacting propane-1,2-diol with excess acidified potassium dichromate(VI). The reaction mixture is heated under reflux. Write an equation for this oxidation. Use [O] to represent the oxidising agent and show structural formulae for organic compounds.OCR 2013 [2]<br />
 (c) Pyruvic acid can also be reduced by NaBH4 to form CH3CH(OH)COOH. Outline the mechanism for this reduction. Use curly arrows and show relevant dipoles. (d) Compound A, shown below, is a structural isomer of pyruvic acid. [4] OH compound A Describe a chemical test that could be carried out in a laboratory to distinguish between samples of pyruvic acid and compound A. Your answer should include reagents, observations, the type of reaction and the organic product formed. In your answer, you should use appropriate technical terms, spelled correctly.[3]OCR 2013 Turn over<br />
 (e) Compound B is an organic compound used to make some cosmetics. Compound B contains C, H and O only. Elemental analysis shows that B has the percentage composition by mass: C, 55.81%; H, 7.02%; O, 37.17%. The mass spectrum of compound B is shown below. 100 relative intensity 80 60 40 20 10 20 30 40 50 60 m / z 70 80 90 100 110 120 (i) Determine the molecular formula of compound B. Show all of your working. molecular formula of compound B =[2]OCR 2013<br />
 (ii) Compound B is an E-stereoisomer. Compound B effervesces with aqueous Na2CO3 to form organic compound C. Compound B decolourises Br2 to form compound D. Compound B polymerises to form polymer E. In the boxes below:draw structures for compounds B, C and D.draw one repeat unit for polymer E. compound B compound C compound D one repeat unit of polymer E [4] [Total: 17] Turn overOCR 2013<br />

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