Chiral

Chiral Chirality is a geometric property of some molecules and ions. A chiral molecule or ion is non-superimposable on its mirror image. The term "chiral" is derived from the Greek word for hand, "cheir," which is a common example of an object with chirality. In chemistry, chirality is an important concept in stereochemistry and is crucial in the field of organic chemistry.

Chirality in Chemistry

In chemistry, chirality usually refers to molecules. A chiral molecule has a non-superimposable mirror image, much like how left and right hands are mirror images but cannot be perfectly aligned on top of each other. These mirror images are called enantiomers. Enantiomers have identical physical properties except for their interaction with plane-polarized light and reactions in a chiral environment.

Chiral Centers

A common source of chirality in molecules is the presence of a chiral center, typically a carbon atom with four different substituents. This carbon atom is also known as an asymmetric carbon or stereocenter. The arrangement of these substituents in space leads to two non-superimposable configurations, known as the R and S configurations, based on the Cahn-Ingold-Prelog priority rules.

Optical Activity

Chiral molecules are often optically active, meaning they can rotate the plane of polarized light. This property is measured using a polarimeter and is expressed as either dextrorotatory (clockwise rotation) or levorotatory (counterclockwise rotation). The specific rotation is a characteristic property of a chiral substance.

Chirality in Nature

Chirality is a fundamental aspect of many biological molecules and processes. For example, most amino acids (the building blocks of proteins) and sugars are chiral. In biological systems, only one enantiomer of a chiral molecule is usually active or functional. This selectivity is crucial for the structure and function of biomolecules.

Applications of Chirality

Chirality has significant implications in various fields, including pharmacology, materials science, and nanotechnology. In pharmacology, the two enantiomers of a chiral drug can have different effects in the body. One enantiomer may be therapeutically beneficial, while the other could be inactive or even harmful. Therefore, the development of chiral drugs often involves the separation and study of individual enantiomers.

Related Concepts

• Stereoisomerism
• Diastereomers
• Racemic mixture
• Chiral resolution
• Enantioselective synthesis

See Also

• Stereochemistry
• Molecular symmetry
• Optical isomerism
• Chiral ligand
• Chiral chromatography