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Three-Dimensional Representations

Assigning Priorities

Determining Stereochemical Relationships

Question Sets

A project of the Chemical Education Digital Library

For example, S-thalidomide is a sedative and helps to reduce morning sickness in pregnant women. R-thalidomide causes birth defects. R and S are used to denote the stereochemistry of a molecule.

In the past, thalidomide was given to pregnant women to lessen their morning sickness. Sadly, many babies were born with birth defects because of the harmful effects of one form of this molecule.

This tutorial is designed to help you master the concept of stereochemistry. There are sections on definitions, different three-dimensional representations, assigning priorities to stereocenters, and determining the stereochemical relationship between molecules. Each section will be followed by a question set, so that you can test your knowledge. Several comprehensive question sets can be found at the end of this tutorial.

You do not need to go through every section in this tutorial. You can select the sections that will be most beneficial to you; the remaining sections can be used as a reference. However, information covered in earlier sections will be assumed in later sections.

The rotating "ball-and-stick" type models at the top of this page are called JMol images. JMol images will be used throughout this tutorial to help you visualize how certain two-dimensional structures look in three dimensions. Occasionally, two JMol images will be shown side-by-side in order for you to make a comparison between three-dimensional molecules. The rotation of all of the JMol images can be stopped by clicking the "spin off" radio dials. Clicking (and holding) on any JMol image, then moving the mouse will allow you to manually rotate the JMol images. Use the JMol images on this page to familiarize yourself with these controls.

If the text on this page is too small for you to read comfortably, most internet browsers will allow you to enlarge text. (You can also make the text smaller if it is too large for your tastes.) Adjust your browser's settings now so that you can comfortably read the text before working through the tutorial.

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