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16 7* Organic compound C has the following percentage composition by mass: C, 54.5%; H, 9.1%; O, 36.4%. The infrared spectrum and mass spectrum of compound C are shown below. 100 transmittance 50 (%) 0 4000 3000 1000 2000 1500 wavenumber / cm–1 500 100 80 relative intensity 60 40 20 0 10 20 30 40 50 m /z 60 70 80 90 In the mass spectrum, a secondary carbocation is responsible for the peak with the greatest relative intensity. © OCR 2016 17 Identify compound C. In your answer you should make clear how your conclusion is linked to all the evidence. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [6] END OF QUESTION PAPER © OCR 2016 16 7* Compound F is a trans stereoisomer which is a useful intermediate in organic synthesis. The results of elemental and spectral analysis of compound F are shown below. Percentage composition by mass: C, 68.6 %; H, 8.6 %; O, 22.8 %. Infrared spectrum 100 transmittance (%) 50 0 4000 3000 2000 1500 wavenumber / cm–1 500 1000 Mass spectrum 100 80 60 relative intensity 40 20 0 10 20 30 40 50 m /z © OCR 2018 60 70 80 17 In the mass spectrum, the peak with the greatest relative intensity is caused by the loss of a functional group from the molecular ion of compound F. Determine the structure of compound F. Explain your reasoning and show your working. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [6] END OF QUESTION PAPER © OCR 2018 PMT 21 7 A student was provided with a mixture of two structural isomers. Each isomer has the percentage composition by mass C, 29.29%; H, 5.70%; Br, 65.01%. The relative molecular mass of each isomer is less than 150. (a) Determine the structures of the two structural isomers. Show your working. In your answer you should link the evidence with your explanation. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... [5] © OCR 2016 Turn over PMT 22 (b) The student heats the mixture of the two structural isomers from (a) under reflux with aqueous sodium hydroxide to form two compounds, E and F. The student separates the two compounds. Compound E is heated under reflux with acidified potassium dichromate(VI) to form compound G, which gives the infrared spectrum below. 100 transmittance (%) 50 0 4000 3000 2000 wavenumber / (i) 1500 1000 500 cm–1 Analyse the information and spectrum to determine the structures of E, F and G. Include an equation for the formation of G from E. In your answer you should link the evidence with your explanation. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... © OCR 2016 PMT 23 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [6] (ii) Compound G is heated with compound F in the presence of a small amount of concentrated sulfuric acid to form organic compound H. Draw the structure of the organic compound H. [2] [Total: 13] END OF QUESTION PAPER © OCR 2016 11 5 Propanoic acid, CH3CH2COOH, is a member of the homologous series of carboxylic acids. (a) Suggest the general formula for a carboxylic acid. .............................................................................................................................................. [1] (b) The displayed formula for propanoic acid is shown below. H (i) H H C C H H O C O H State the shape and bond angle around a carbon atom in the alkyl group of propanoic acid. Explain the shape. Shape ................................................................................................................................ Bond angle ........................................................................................................................ Explanation ....................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2] (ii) Suggest a value for the C–O–H bond angle in propanoic acid. ...................................................................................................................................... [1] © OCR 2017 Turn over 12 (c) Compound D is a neutral compound which is a structural isomer of propanoic acid, CH3CH2COOH. The infrared spectrum of compound D is shown below. Item removed due to third party copyright restrictions. peak at at peace 1700 3300 cm 1 on Suggest two possible structures of compound D. Explain all your reasoning. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [4] © OCR 2017 13 (d) 2-Chloropropanoic acid, CH3CHClCOOH, can be made by reacting propanoic acid with chlorine in a radical substitution reaction. (i) State the conditions for the reaction. ...................................................................................................................................... [1] (ii) Write the overall equation for the reaction. ...................................................................................................................................... [1] (iii) The first step in the reaction mechanism involves homolytic fission of a chlorine molecule to form two chlorine radicals. Why is this step an example of homolytic fission? ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [1] (iv) Write two equations to show the propagation steps in the mechanism for this reaction. Use dots,•, to show the unpaired electrons on radicals. ........................................................................................................................................... ...................................................................................................................................... [2] (v) Draw the displayed formula of the radical formed in the first propagation step. Use a dot,•, to show the position of the unpaired electron. [1] (vi) Further substitution forms a mixture of organic products. Draw the structure of an organic product formed from 2-chloropropanoic acid by further substitution. [1] © OCR 2017 Turn over