Steric factors

Abstract

The size and shape of a molecule can play a very important part in its biological action. For some types of action a flat molecule is required, whereas other types of action require a three-dimensionally bulky molecule. The benzene ring(12.1) is flat, and the six bonds leading from the ring to all attached atoms or groups also lie in the plane of the paper. All other conjugated systems (i.e. those where every second bond is a double bond) are similarly flat.