Achiral

Achiral is a term used in chemistry to describe a molecule that is superimposable on its mirror image. This means that the molecule does not have chirality, which is a property where a molecule and its mirror image are not superimposable. Achiral molecules do not exhibit optical activity, meaning they do not rotate the plane of polarized light.

Characteristics

Achiral molecules can be identified by the presence of a plane of symmetry or a center of symmetry. These symmetry elements ensure that the molecule and its mirror image are identical. In contrast, chiral molecules lack these symmetry elements and exist as two non-superimposable mirror images, known as enantiomers.

Examples

Common examples of achiral molecules include:

• Methane (CH₄)
• Ethane (C₂H₆)
• Benzene (C₆H₆)

These molecules have symmetrical structures that make them superimposable on their mirror images.

Applications

Understanding whether a molecule is achiral or chiral is crucial in various fields such as pharmacology, biochemistry, and materials science. For instance, the chirality of a drug molecule can significantly affect its interaction with biological targets, leading to different therapeutic effects.

Related Concepts

• Chirality (chemistry)
• Enantiomer
• Diastereomer
• Optical isomerism
• Symmetry in chemistry

See Also

• Stereochemistry
• Molecular symmetry
• Optical activity
• Chiral resolution