Wize University Organic Chemistry Textbook > Stereochemistry & Isomers
Stereoisomers I - Conformational Isomers
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Conformational Isomers
Conformational Isomers
Conformational isomers have the same molecular formula and bond connectivity but are isomers by bond rotation.
The most common examples in organic chemistry are alkanes and are usually shown using Newman projections or Fisher projections.
Watch Out!
Conformational isomers are just the same molecule with the rotation around a single bond (i.e. they are never present when there is a pi bond).
Energetics of Conformational Isomers
Due to steric interactions different conformers (conformational isomers) are favoured for enthalpic reasons. Let's look at butane for example:
When we look at the Newman projections of butane we see some projections with larger steric interactions and higher relative energy. The main conformations are either staggered (1, 3, 5) and eclipsed (2, 4, 6). In the staggered orientation the methyl groups can either be anti (3) or gauche (1, 5).
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Example: Conformational Isomers
Draw both conformational isomers of the cyclohexane ring shown below.
