NYJC_H3_Chemistry_P1

[Turn over NANYANG JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 3 PHARMACEUTICAL CHEMISTRY 9812/01 Paper 1 29 September 2014 2 hours 30 minutes Additional Materials: Answer Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. 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 five questions. 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 17 printed pages and 1 blank page.

2 H3 Chemistry 9812/01 NYJC J2/14 PX [Turn over 1(a) Propranolol was the first successful beta blocker developed to treat hypertension. It was developed by the British scientist James W. Black in the 1960s. In 1988, he was awarded the Nobel Prize in Medicine for this discovery. Propranolol acts as an antagonist to the -adrenergic receptors in the smooth muscle tissues of the heart. propranolol (i) Describe what is meant by the terms agonist and antagonist. [2] Propranol is sold as a racemate, a mixture of two isomers. The (R) -enantiomer is the beta-blocker for the heart and the (S)-enantiomer is a contraceptive. (ii) Suggest why propranolol is sold as a racemate , even though only one of its enantiomers is useful for treating hypertension. [1] (iii) Draw the two optical isomers of propranolol. [2] (iv) Suggest a method to separate the two isomers. [2] Propranolol can be synthesised by the following two routes: (v) Suggest a mechanism for either one of the routes. [4]

3 H3 Chemistry 9812/01 NYJC J2/14 PX [Turn over (b) Atenolol is another beta -blocker that was developed much later, in 1976, as a replacement for propranolol. Unlike propranolol, it does not pass through the blood-brain barrier easily thus avoiding various central nervous system side effects. atenolol (i) Outline the processes that are likely to occur when propranolol crosses the blood-brain barrier at physiological pH 7.4. [3] (ii) Suggest why atenolol crosses the blood -brain barrier less easily than propranolol. [1] (c) Adrenaline (also known as epinephrine) is a hormone and a neurotransmitter . Bucumolol is a -adrenergic blocking agent, like propranolol. adrenaline