OCR A Jun 2015 Paper 4 Q4

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4 A student reacts compound K with 2,4-dinitrophenylhydrazine. An orange precipitate, L, was formed. 15 R1 R2 (cid:70)(cid:82)(cid:80)(cid:83)(cid:82)(cid:88)(cid:81)(cid:71)(cid:3)(cid:46) O2N NO2 H2N (cid:21)(cid:15)(cid:23)(cid:16)(cid:71)(cid:76)(cid:81)(cid:76)(cid:87)(cid:85)(cid:82)(cid:83)(cid:75)(cid:72)(cid:81)(cid:92)(cid:79)(cid:75)(cid:92)(cid:71)(cid:85)(cid:68)(cid:93)(cid:76)(cid:81)(cid:72) O2N R1 R2 NO2 H2O (cid:82)(cid:85)(cid:68)(cid:81)(cid:74)(cid:72)(cid:3)(cid:83)(cid:85)(cid:72)(cid:70)(cid:76)(cid:83)(cid:76)(cid:87)(cid:68)(cid:87)(cid:72)(cid:3)(cid:47) The student purifies the orange precipitate, L, and sends the sample for analysis using 1H NMR and 13C NMR spectroscopy. (a) Describe a use for NMR spectroscopy in medicine.[1] (b) (i) State the region of the electromagnetic spectrum used in 1H NMR spectroscopy.[1] (ii) Explain why CDCl3 is used as a solvent in 1H NMR spectroscopy.[1] (c) The 13C NMR spectrum of L is shown below. 180 160 140 120 100 80 60 40 20 chemical shift, / ppm How many different carbon environments (types of carbon) are present in a molecule of compound L?[1]OCR 2015 Turn over<br />
 (d) The reaction of K to form L is repeated below. 16 R1 R2 (cid:70)(cid:82)(cid:80)(cid:83)(cid:82)(cid:88)(cid:81)(cid:71)(cid:3)(cid:46) O2N NO2 H2N (cid:21)(cid:15)(cid:23)(cid:16)(cid:71)(cid:76)(cid:81)(cid:76)(cid:87)(cid:85)(cid:82)(cid:83)(cid:75)(cid:72)(cid:81)(cid:92)(cid:79)(cid:75)(cid:92)(cid:71)(cid:85)(cid:68)(cid:93)(cid:76)(cid:81)(cid:72) The 1H NMR spectrum of L is shown below. O2N R1 R2 NO2 H2O (cid:82)(cid:85)(cid:68)(cid:81)(cid:74)(cid:72)(cid:3)(cid:83)(cid:85)(cid:72)(cid:70)(cid:76)(cid:83)(cid:76)(cid:87)(cid:68)(cid:87)(cid:72)(cid:3)(cid:47) 10 5 chemical shift, / ppm Use your answer to (c) and the data given to identify R1, R2 and the structure of compound L. Explain how you used the chemical shifts and splitting patterns in the 1H NMR spectrum and any evidence from the 13C NMR spectrum. In the 1H NMR spectrum, HCC=N would have a peak in the range= 1.62.2 ppm. In your answer, you should use appropriate technical terms, spelled correctly.OCR 2015<br />
 17structure of compound L [7] (e) Draw the structure of compound K. structure of compound K [1] [Total: 12]OCR 2015 END OF QUESTION PAPER<br />

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