2023 EJC H2 Chem Prelims Paper 3_QP

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2023 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 2 – INDEX NUMBER CHEMISTRY Paper 3 Free Response 9729/03 18 September 2023 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staplers, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all questions. Section B Answer one question. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Paper 3 A1 / 19 A2 / 23 A3 / 18 B4 or 5 / 20 Total / 80 This document consists of 32 printed pages.

2 © EJC 9729/03/J2PE/23 Section A Answer all the questions in this section. 1 (a) Solvolysis is a reaction in which the solvent is one of the reagents and is also present in great excess of that required for the reaction. Usually, the electron -rich solvent molecule substitutes an atom or group in the reactant molecule. One example of solvolysis is the reaction of compound A, C6H5CH2Br, with ethanoic acid as the solvent. Br A + OH O O O + HBr This reaction happens via an SN1 mechanism. (i) Describe the mechanism for the reaction between compound A with ethanoic acid. Show relevant lone pairs of electrons, dipoles and curly arrows. [4] (ii) Explain why this reaction mainly proceeds via the SN1 mechanism. [1] (iii) Given that the enthalpy change of the reaction is endothermic, draw a labelled reaction pathway diagram for the reaction involving compound A and ethanoic acid. [2] Another reaction was carried out using C6H5CHBrCH3 with ethanol as the solvent, in the presence of trace amount of sodium hydroxide. This reaction undergoes the same mechanism as the reaction between compound A and ethanoic acid. (iv) Predict the major organic product formed from the reaction of optically pure C6H5CHBrCH3 with ethanol, and comment on the optical activity of the product formed. Briefly explain your answer. [3] (v) By-products are formed during the preparation of many organic compounds. This usually occurs because the reagents can react in more than one way. Suggest a possible by-product, in full structural formula, that can be formed from the above reaction. [1] .............................................................