CIE Jun 2017 v2 Paper 2 Q4

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(a) The hydrocarbons A, C4H10, and B, C4H8, are both unbranched. PMT A does not decolourise bromine. B decolourises bromine and shows geometrical isomerism. (i) Draw the skeletal formula of A. [1] (ii) The hydrocarbon A, C4H10, has a branched isomer. Suggest why unbranched A has a higher boiling point than its branched isomer.[2] (iii) Give the structural formula of B.[1] (iv) Explain why B shows geometrical isomerism.[2]UCLES 2017 9701/22/M/J/17<br /> (v) Draw the mechanism of the reaction of B with bromine, Br2. Include all necessary charges, dipoles, lone pairs and curly arrows. PMT (vi) Explain the origin of the dipole on Br2 in this mechanism.[1] [4] (b) The alcohols C and D are isomers of each other with molecular formula C4H10O. Both isomers are branched. When C is heated under reflux with acidified potassium dichromate(VI) no colour change is observed. When D is heated under reflux with acidified potassium dichromate(VI) the colour of the mixture changes from orange to green and E, C4H8O2, is produced. E reacts with aqueous sodium carbonate to form carbon dioxide gas. (i) Identify C, D and E. [3] (ii) Write the equation for the reaction between E and aqueous sodium carbonate.[1]UCLES 2017 9701/22/M/J/17 [Turn over<br /> PMT 10 (c) The isomers F and G, C5H10O, both form an orange precipitate when reacted with 2,4-DNPH. F is unbranched and reacts with alkaline aqueous iodine to produce a yellow precipitate. G does not react with alkaline aqueous iodine. It contains a chiral centre and produces a silver mirror when warmed with Tollens reagent. (i) Name the yellow precipitate produced by the reaction between F and alkaline aqueous iodine.[1] (ii) Give the structural formula of F and of G. FG[2] (iii) Explain the meaning of the term chiral centre.[1]UCLES 2017 9701/22/M/J/17<br /> 11 (d) H and I are isomers with molecular formula C2H4O2. The infra-red spectra of isomers H and I are shown. 100 PMT percentage transmittance 50 0 4000 100 3000 2000 wavenumber / cm1 1500 1000 percentage transmittance 50 0 4000 3000 2000 wavenumber / cm1 1500 1000 (i) Identify the bonds responsible for the principal peaks above 1500 cm1 in each spectrum. spectrum of Hspectrum of I[2] (ii) Name H and I. HI[2]UCLES 2017 9701/22/M/J/17 [Total: 23] [Turn over<br />

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