Organic and Inorganic Chemistry Lesson of the Day – Stereogenic Centre
July 2, 2014 Leave a comment
A stereogenic centre (often called a stereocentre) is an atom that satisfies 2 conditions:
- it is bonded to at least 3 substituents.
- interchanging any 2 of the substituents would result in a stereoisomer.
If a molecule has only 1 stereogenic centre, then it definitely has a non-superimposable mirror image (i.e. this molecule is chiral and is an enantiomer). However, depending on its stereochemistry, it is possible for a molecule with 2 or more stereogenic centres to be achiral; such molecules are called meso isomers (or meso compounds), and I will discuss them in a later lesson.
In organic chemistry, the stereogenic centre is usually a carbon atom that is attached to 4 substituents in a tetrahedral geometry. In inorganic chemistry, the stereogenic centre is usually the metal centre of a coordination complex.
In organic chemistry, stereogenic centres with substituents in a tetrahedral geometry are common. Inorganic coordination complexes can also have a tetrahedral geometry. A stereoisomer with tetrahedral stereogenic centres can have at most stereoisomers. The “at most” caveat is important; as mentioned above, it is possible for a molecule with 2 or more stereogenic centres to have a spatial arrangement that results in having a superimposable mirror image; such isomers are meso isomers. I will discuss meso isomers in more detail in a later lesson.