enantiomeric excess

Enantiomeric excess (ee) is a measure of how much one mirror-image form of a compound (called an enantiomer) dominates over the other in a mixture. Since enantiomers are like left and right hands—they are similar but non-superimposable—their presence affects properties like how substances interact with biological systems. A 0% ee means equal amounts of both enantiomers, while 100% ee means only one enantiomer is present. This concept is important in chemistry, especially in drug development, as different enantiomers can have different effects or activities.