Enantiomers are optical isomers that are non-superimposable mirror images about a chiral centre.

For example, the enantiomers of lactic acid are shown below.

Enantiomers rotate plane-polarised light in opposite directions; one rotates it clockwise, and the other rotates it anti-clockwise.

A chiral centre is a carbon atom in a molecule bonded to four different atoms or groups.

Chiral centres are often indicated on formulae by an asterisk (*).

A molecule is considered optically active if it has the ability to rotate the plane of polarised light due to its chiral structure.

A racemic mixture is an equal mixture of two enantiomers of a chiral compound.

A racemic mixture is also called a racemate.

Racemic mixtures are optically inactive because the rotations caused by the two enantiomers cancel each other out.

Since there are equal amounts rotating clockwise and anti-clockwise, the net rotation is zero and no optical activity is observed.

1. Enantioselectivity - Chiral catalysts selectively produce the desired enantiomer, minimizing the formation of the unintended enantiomer that may be inactive or even harmful.
2. Efficiency - By directly synthesizing the target enantiomer, chiral catalysts eliminate the need for costly and time-consuming post-synthesis separation of enantiomers, streamlining the production process.
3. Safety - The selective production of the therapeutically active enantiomer reduces the risk of adverse effects associated with the presence of the inactive or toxic enantiomer in the final drug product.
4. Cost-effectiveness - Chiral catalysts improve the overall economy of the manufacturing process by increasing yield, reducing waste, and avoiding the need for additional purification steps.

Optical isomerism is a type of stereoisomerism where isomers have the same structural formula but different arrangements of atoms in space.

Optical isomers can be distinguished by their ability to rotate plane-polarised light in opposite directions. One optical isomer rotates it clockwise, while the other rotates it anti-clockwise.