Chemguide: Support for CIE A level Chemistry

Learning outcome 13

13.4: Isomerism: structural and stereoisomerism

Statements 13.4.2, 13.4.4 and 13.4.5

These statements talk about optical isomerism, a form of stereoisomerism.

Before you go on, you should find and read the statements in your copy of the syllabus.

You will find this discussed in detail on the page about optical isomerism.

There are some things on this page that you can miss out, because CIE don't what anything about the background to optical isomerism, such as plane polarised light.

  • Read the "What is stereoisomerism?" section. (Although you have probably read this already on the cis-trans isomerism page.)

  • Skip the section headed "Why optical isomers?". It would, however, be useful if you knew that optical isomers are referred to as enantiomers. That isn't for CIE purposes (they don't seem to use the term), but I shall use the word further down the page, and you need to know what I am talking about.

    For the same reason, you also need to know that one isomer is referred to as the (+) form and the other the (-) form. Again, I use these terms further down the page, but you won't need them for CIE exams.

  • Now read on from "How optical isomers arise". Continue down as far as the diagrams showing the two enantiomers of 2-aminopropanoic acid (alanine). You do not need to bother about the text underneath this diagram.

  • Now read the rest of the page starting from "Identifying chiral centres in skeletal formulae"

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© Jim Clark 2020