SAJC 2022 P3 ANS

1 [TURN OVER ST ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS HIGHER 2 CANDIDATE NAME CLASS 2 1 S CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 14 September 2022 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class on all the work that you hand in. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, 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. This document consists of 26 printed pages (including this cover page). For Examiner’s Use Q1 21 Q2 19 Q3 20 Q4 or Q5 20 Total 80

2 [TURN OVER 1 (a) The diagram below shows how compound E may be prepared. CH3 CH3 Br Compound A O CH3 O CH3 Br Step 1 Step 2 Br O Compound B Compound C Compound D Compound E conc H2SO4 heat (i) Draw the structural formulae for C and D. [2] Compound C: OH CH3 CH3 Compound D: O OH Br (ii) Suggest the reagents and conditions for steps 1 and 2. [2] Step 1: aq NaOH, heat Step 2: aq H2SO4,aq KMnO4, heat

3 [TURN OVER or aq H2SO4 K2Cr2O7, heat (iii) Draw the structures of the products formed when E is reacted with hot aqueous sodium hydroxide. [2] CH3 CH3 OH O OH OH - (nucleophilic substitution for bromoalkane will occur) (iv) State the type of reaction when C and D react to form E. [1] Condensation / nucleophilic (acyl) substitution (v) Equal amounts of A, F and G are added separately to three test-tubes, which each contains equal concentration of ethanolic silver nitrate. The test-tubes are placed in a hot water bath. No precipitate is formed in one of the test-tubes. For the other two test-tubes, precipitates are formed at different rates. Explain these observations. CH3 CH3 Compound G CH3 CH3 I Compound F Cl [3] Compounds A and F undergo nucleophilic substitution with ethanolic AgNO3 which releases halide ion to form a ppt with Ag+. C−I bond in F is weaker than C−Br bond in A as I is larger atom than Br and has less effective orbital overlap with C. Thus Iꟷ is released faster to form ppt, followed by Brꟷ. Lone pair of electrons on the Cl atom delocalise into the π bond / C=C, resulting in C–Cl having partial double bond character, hence the bond does n