OCR A Jun 2017 Paper 2 Q20

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26 20 A chemist analyses a naturally occurring aromatic compound. (a) The percentage composition and mass spectrum of the compound are shown below. Percentage composition by mass: C, 70.58%; H, 5.92%; O, 23.50%. Mass spectrum 100 relative intensity 80 60 40 20 m /z Determine the molecular formula of the compound. Show your working. 25 50 75 100 125 150 (b) Qualitative tests are carried out on the aromatic compound. The results are shown below. molecular formula =[3] Test Observation Acidity pH = 5 Na2CO3(aq) No observable change 2,4-DNP Tollens reagent Orange precipitate No observable change Determine the functional groups in the compound. Explain your reasoning. Functional groupsExplanation[3]<br /> (c) The carbon-13 NMR spectrum of the compound is shown below. 27 200 180 160 140 120 100 chemical shift, / ppm 80 60 40 20 Using the spectrum and the results from (a) and (b), determine the structure of the compound. Explain your reasoning.Structure of compound [3]<br />

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