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Three-Dimensional Representations

Assigning Priorities

Determining Stereochemical Relationships

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Definitions: Enantiomers

Now that chirality within a molecule has been discussed, the relationships between two or more chiral molecules can be determined.

Enantiomers are chiral molecules that are mirror images of one another. Furthermore, the molecules are non-superimposable on one another. This means that the molecules cannot be placed on top of one another and give the same molecule. Chiral molecules with one or more stereocenters can be enantiomers. It is sometimes difficult to determine whether or not two molecules are enantiomers. For introductory purposes, simple molecules will be used as examples. More complex examples will be given later.

For example, consider the following molecules.

These molecules are mirror images of one another. Additionally, these molecules are non-superimposable because if one of these molecules, the one on the right, is flipped 180 degrees (so that the chlorines are aligned, as shown below), the stereochemistry is different (one chlorine is wedged and the other is dashed). Therefore, these molecules are enantiomers. (Note: When flipping molecules using the Wedge-Dash notation, groups that are wedged become dashed, and groups that are dashed become wedged.)

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