2009 RI H3 Chemistry Prelims P1 Questions

3 © Raffles Institution (Junior College) 2009 [Turn over RAFFLES INSTITUTION (JUNIOR COLLEGE) PRELIMINARY EXAMINATION 2009 HIGHER 3 PHARMACEUTICAL CHEMISTRY 9812/01 Paper 1 28 September 2009 2 hour 30 minutes Additional Materials: Answer Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your index number, civics tutorial grou p and name on the Cover Page and all the writing paper you hand in. Write in dark blue or black pen on both sides of the writing 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 five questions. Begin each question on a fresh sheet of paper. 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. You may use a calculator. You are reminded of the need for clear presentation in your answers. This document consists of 16 printed pages.

3 © Raffles Institution (Junior College) 2009 [Turn over Name Index Number CT Group RAFFLES INSTITUTION (JUNIOR COLLEGE) PRELIMINARY EXAMINATION 2009 HIGHER 3 PHARMACEUTICAL CHEMISTRY 9812/01 Attach this Cover Page on top of your answer script. Question Number (Please circle the questions you have attempted.) Marks 1 / 20 2 / 20 3 / 20 4 / 20 5 / 20 6 / 20 Total / 100

3 © Raffles Institution (Junior College) 2009 [Turn over 1 Sulfonamides, or sulfa drugs, are bacteriostatic. They do not kill bacteria, but merely stop them from growing and dividing. SO2NHRNH2 sulfonamide The R group can be varied by incorporating a large range of heterocyclic or aromatic structures. Varying the R group affects the solubility of sulfonamides or the extent to which they bind to plasma protein, but not the mode of action of the drug. (a) Sulfapyridine is a good antibacterial drug, but its solubility in water is very pH dependent. NH O O SNH2 N sulfapyridine (i) Outline the mode of action of sulfapyridine. [2] (ii) Explain why sulfapyridine does not affect human cells. [2] (iii) Use the concept of solubility to suggest why sulfapyridine is no longer prescribed for treatment in humans. [2] (b) When sulfapyridine interacts with its target receptor, the binding interactions are non-covalent in nature. (i) Describe three important types of interaction that take place at the receptor site in side the human body. [2] (ii) Identify the groups on sulfapyridine that are capable of ma