DHS Prelim_H2_CHEM_P3_QP

This question paper consists of 15 printed pages and 1 blank page. © DHS 2016 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination 2016 Year 6 H2 CHEMISTRY 9647/03 Paper 3 Free Response 20 September 2016 2 hours Additional Materials: Data Booklet Writing Papers Graph Paper INSTRUCTIONS TO CANDIDATES Write your name, index number and class on this question paper and on the Cover Sheet provided. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. Start each question on a fresh sheet of paper. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination:  Fasten all work securely together with the Cover Sheet on top.  Hand in the question paper separately. The total marks for this paper is 80 marks.

2 © DHS 2016 9647/03 [Turn over Answer any four questions. 1 Blue #1 (Na2C37H34N2S3O9) is a synthetic food colouring often found in ice cream. (a) One of the main compounds used to produce Blue #1 is benzenesulfonic acid, which is produced by heating benzene under reflux with concentrated sulfuric acid for several hours. (i) The first step of the mechanism involves the protonation of one molecule of sulfuric acid by another and the loss of a molecule of water. Name the type of reaction and describe the mechanism. In your answer, show relevant lone pairs and charges, and use curly arrows to indicate the movement of electrons. [4] (ii) Benzenesulfonic acid is a useful starting material as it can be easily converted to phenol by heating with NaOH(aq) at 300°C followed by acidification. It also has similar chemical reactivity as nitrobenzene.  H2SO4 H2O 3000C HCl (aq)

3 © DHS 2016 9647/03 [Turn over Compound A can be synthesised from either benzenesulfonic acid or ethylbenzene in not more than 4 steps. A The first step of the synthesis using either benzenesulfonic acid or ethyl benzene is as shown below in Scheme 1 and 2 respectively: Scheme 1: Scheme 2: Identify the correct scheme that will give compound A and copy the synthetic scheme in your answer. Using information in (a)(ii), suggest the next three steps to synthesise compound A. Show all intermediates, reagents and conditions clearly in your synthetic route. [4] CH3CH2Cl / AlCl3 CH2CH3 CH2CH3 conc. H2SO4 heat CH2CH3

4 © DHS 2016 9647/03 [Turn over (