Illustrated Glossary of Organic Chemistry

Steric effect: Any effect on a molecule, a reaction, etc. due to the size of atoms or groups. Common steric effects include steric hindrance and van der Waals repulsion.

In this cyclohexane chair flip equilibrium, K_eq > 1. This is an example of a steric effect caused by van der Waals repulsion: the tert-butyl group is larger (and therefore causes more van der Waals repulsion) than the methyl group.


This S_N2 reaction occurs at a primary carbon but not a tertiary carbon. This is an example of a steric effect caused by steric hindrance: the tertiary carbon is more hindered than the primary carbon.