2019 HCI Prelim H2 Chem P3 QP

This document consists of 11 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 18S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on separate answer booklet. Additional Materials: 12-Page Answer Booklet Data Booklet 9729/03 20 September 2019 2 hours READ THESE INSTRUCTIONS FIRST Write your name, CT group, centre number and index number on all the work 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. Section A Answer all questions. Section B Answer one question. Begin each question on a new page of writing paper. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the paper, submit only the 12-Page Answer Booklet and any additional booklets you have used.

2 © Hwa Chong Institution 2019 9729 / 03 / C2 Prelim 2019 Section A Answer all the questions in this section. 1 (a) (i) Write an equation for the thermal decomposition of MgCO3. [1] (ii) Explain how the magnitude of the lattice energy of MgCO3 differs from that of the solid product formed in (a)(i). [2] (iii) The thermal decomposition of MgCO3 is an endothermic process. Explain whether the decomposition of MgCO3 is spontaneous at high or low temperature. [2] (iv) State whether MgCO 3 or BaCO 3 has the lower decomposition temperature. Explain your answer. [3] (b) The Strecker synthesis is a method used to prepare amino acids. Alanine, 2-aminopropanoic acid, can be prepared from ethanal via Strecker synthesis as shown below. (i) Suggest the type of reaction occurring in steps 1 and 2. [2] (ii) Draw the fully displayed structure of compound E. [1] (iii) Suggest why step 3 produces an equimolar mixture of two stereoisomers. [2] (iv) Another amino acid, isoleucine, can be prepared from aldehyde F via Strecker synthesis. isoleucine Draw the structure of aldehyde F. [1]

3 © Hwa Chong Institution 2019 9729 / 03 / C2 Prelim 2019 (c) In the Petasis reaction, carbonyl compounds, amines and suitable boronic acids can react to form substituted amines. The general structure of a boronic acid is B(OH)2R where R is an alkyl or aryl group. An example of the Petasis reaction is given below. Consider the following Petasis reaction: (i) Draw the structure of compound G. [1] (ii) The Petasis reaction can be used in step 4 of the following s