16 8 This question is about some reactions of cyclohexanol. cyclohexene cyclohexanol potassium dichromate(VI) in dilute sulfuric acid B A 50 % concentrated sulfuric acid and potassium bromide (a) Write the skeletal formula of compound A. (1) (b) (i) Give the name and displayed formula of compound B. (2) Turn over 17 (ii) The infrared (IR) spectra of cyclohexanol and compound B are shown. IR Spectrum of cyclohexanol Transmittance / % 100 50 0 4000 Wavenumbers / cm–1 3000 2000 1500 1000 100 IR Spectrum of compound B Transmittance / % 100 50 0 4000 Wavenumbers / cm–1 3000 2000 1500 1000 100 Identify the bonds, using both IR spectra, that help to confirm the reaction of cyclohexanol to produce compound B. Your answer must include the wavenumber ranges of any relevant bonds. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 18 (iii) The mass spectrum of compound B is shown. Relative intensity 100 80 60 40 20 0 10 20 30 40 50 60 70 80 90 100 m/z Deduce the relative molecular mass of compound B using the mass spectrum. Justify your answer. 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(iv) In the mass spectrum of cyclohexanol, there is a peak at m/z = 83. Give the formula of a fragment that could be responsible for this peak. (2) Turn over 19 (c) (i) Cyclohexanol can be converted to cyclohexene. What is the classification for this reaction? (1) A addition B elimination C oxidation D substitution (ii) In an experiment, 10.0 cm3 of cyclohexanol was converted to cyclohexene with a 63.0 % yield. Compound Molar mass / g mol–1 Density / g cm–3 cyclohexanol 100 0.962 cyclohexene 82.0 0.811 Calculate the volume of cyclohexene produced. (4) 20 *(iii) Cyclohexene can be prepared by reacting cyclohexanol with phosphoric(V) acid. The mixture is warmed in a water bath for 15 minutes before distilling off a mixture of cyclohexene and water. Devise a procedure to obtain a pure, dry sample of cyclohexene from the distillate. Include a reason for each step. [ Boiling temperature of cyclohexene = 83 °C Density of cyclohexene = 0.811 g cm–3] (6) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 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(Total for Question 8 = 19 marks)