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23 Organic synthesis
This topic introduces the strategies used in synthesis of organic molecules.
learning outcomes Candidates should be able to:
23.1 Synthesis of chiral drug molecules
a state that most chiral drugs extracted from natural sources often contain only a single optical isomer
b state reasons why the synthetic preparation of drug molecules often requires the production of a single optical isomer, e.g. better
therapeutic activity, fewer side effects
23.2 Synthetic routes a for an organic molecule containing several functional groups:
i identify organic functional groups using the reactions in the syllabus
ii predict properties and reactions b devise multi-stage synthetic routes for preparing organic molecules
using the reactions in the syllabus c analyse a given synthetic route in terms of type of reaction and
reagents used for each step of it, and possible by-products
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4. Practical assessment
4.1 Introduction
Teachers should ensure that learners practise experimental skills throughout the whole period of their course of study. As a guide, learners should expect to spend at least 20 of their time doing practical work
individually or in small groups. This 20 does not include the time spent observing teacher demonstrations of experiments.
The practical work that learners do during their course should aim to: • provide learning opportunities so that learners develop the skills they need to carry out experimental and
investigative work • reinforce their learning of the theoretical subject content of the syllabus
• instil an understanding of the interplay of experiment and theory in scientiic method • prove enjoyable, contributing to the motivation of learners.
Candidates’ experimental skills will be assessed in Paper 3 and Paper 5. In each of these papers, the questions may be based on chemistry not included in the syllabus content, but candidates will be assessed
on their practical skills rather than their knowledge of theory. Where appropriate, candidates will be told exactly what to do and how to do it: only knowledge of theory and experimental skills within the syllabus
will be expected.
Paper 3 is a practical examination that will test the skills of manipulation of apparatus, presentation of data, analysis and evaluation.
Paper 5 is a written examination that will test the higher-order experimental skills of planning, analysis and evaluation. It should be stressed that candidates cannot be adequately prepared for this paper without
extensive laboratory work throughout the course of their study.
Support for teaching practical skills for these qualiications can be found on the Cambridge A Level Support website www.cie.org.ukalevelsupport
Guidance on making measurements and on error analysis may be found on the following website: www.rsc.orgimagesRSCmeasurements_teacher_tcm18-189111.pdf