Enantioselectivity refers to the preference of a chemical reaction to produce one enantiomer over another. Enantiomers are molecules that are mirror images of each other, much like left and right hands. This selectivity is crucial in fields like pharmaceuticals, where the effectiveness and safety of a drug can depend on its specific enantiomer. The degree of enantioselectivity is often measured using the enantiomeric excess (ee), which quantifies the difference in amounts of the two enantiomers produced. Catalysts, such as chiral catalysts, are commonly used to enhance enantioselectivity in reactions, making it possible to favor the desired enantiomer while minimizing the formation of the unwanted one.