13.4.4—Chiral centres and enantiomers

A chiral centre is usually a tetrahedral carbon attached to four different groups. Its mirror-image arrangement cannot be superimposed on the original, giving a pair of optical isomers called enantiomers.

Enantiomers have the same connectivity and most achiral physical properties, but rotate plane-polarised light in opposite directions and can behave differently with chiral environments.

In 2-butanol, the carbon bearing OH is attached to H, OH, CH₃ and CH₂CH₃, so it is chiral and gives two enantiomers.

A carbon with two identical groups is not chiral. Do not add advanced meso or diastereomer terminology when the syllabus does not require it.