OCR A Jun 2010 Paper 4 Q3

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3 A student was given three compounds, an aldehyde, a ketone, and a carboxylic acid. (a) The student carried out the same two chemical tests on each compound. This allowed her to distinguish between all three compounds.Describe two suitable tests that the student could have used. Show how the observations would allow her to distinguish between the compounds.[4] (b) Explain how the student could use infrared spectroscopy to confirm which compound is a carboxylic acid.[1] (c) The aldehyde has the molecular formula C5H10O. The 1H NMR spectrum of the aldehyde contains a doublet at= 0.9 ppm with a relative peak area of six compared with the aldehyde proton. Analyse this information to deduce the structure of the aldehyde. Explain your reasoning.[3]OCR 2010<br />
 (d) The ketone also has the molecular formula C5H10O. There are three structural isomers of this formula that are ketones. (i) Two of these isomers are shown below. Draw the structural formula of the third structural isomer in the box below. CH3 CH2 CH2 CH3 CH3 CH3 CH CH3 ketone 1 ketone 2 ketone 3 [1] (ii) The 13C NMR spectrum of the ketone given to the student is shown below.Use the spectrum to identify the ketone. Explain your reasoning.Identify the carbon responsible for the peak at= 210 ppm. absorption 220 200 180 160 140 120 100 80 60 40 20[3]OCR 2010 [Total: 12] Turn over<br />

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