DHS Prelim_P2_QP

This question paper consists of 21 printed pages and 1 blank page. © DHS 2018 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination 2018 Year 6 H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 13 September 2018 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet INSTRUCTIONS TO CANDIDATES 1 Write your name, index number and class on this cover page. 2 Write in dark blue or black pen. 3 You may use an HB pencil for any diagrams or graphs. 4 Do not use staples, paper clips, glue or correction fluid. 5 Answer all questions in the spaces provided on the Question Paper. The number of marks is given in brackets [ ] at the end of each question or part question. You are advised to show all workings in calculations. You are reminded of the need for good English and clear presentation in your answers. For Examiner’s Use Question No. Marks 1 13 2 12 3 25 4 10 5 15 Total 75

2 © DHS 2018 9729/02 Answer all questions in the spaces provided. 1 Isoprene, E, is an organic compound that could be used to synthesise limonene, which is commonly used in fragrances. (a) E can be synthesised from 3–methylbut–1–ene, A, in a 4–step process as follows. C A E I II III IV HCl (g) B D excess concentrated H2SO4, heat (i) B is a major product of step I. Draw the structures of compounds B, C and D. B C D [3] (ii) Suggest the reagents and conditions for steps II and III. step II : ………………………………………………………….……….………….[1] step III : …………………………………………………………….………………[1] (iii) Predict, with reasoning, whether the mixture of products formed in step I is optically active. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2]

3 © DHS 2018 9729/02 [Turn Over (b) The following reaction shows an alternative route to form intermediates for the synthesis of isoprene, E. Cl Cl F GA + + other products (i) State the reagents and conditions used to form F and G from A. …………………………………………………………………………………….…[1] (ii) Predict the ratio in which F and G will be formed. …………………………………………………………………………………….…[1] (iii) Z was one of the other products formed in the reaction in (b). It was suggested that the radical, •G, is involved in the formation of Z. The mechanism of •G converting to Z is thought to involve 2 steps. 1. Delocalisation of unpaired electron forming • Z. 2. • Z reacts with Cl2 to form Z and a radical. The structures of Z, •G and •Z are as follows. G Z Z Cl Use the information above to draw out the mechanism for the conversion of •G to Z. You are advised to use skeletal or structural formula for all