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Stereocenter
A stereocenter or stereogenic center is an atom bearing groups such that an interchanging of any two groups leads to a stereoisomer.〔Solomons & Fryhle. (2004). Organic Chemistry, 8th ed〕 The most common stereocenters are chiral centers (such as asymmetric carbon atoms) and the double-bonded carbon atoms in cis-trans alkenes.
A chiral center consists of an atom holding a set of ligands (atoms or groups of atoms) in a spatial arrangement which is not superposable on its mirror image. A chiral center is a generalized extension of an ''asymmetric atom''.〔(IUPAC-definition of chirality center )〕 The term stereocenter was introduced in 1984 by Mislow and Siegel.〔''Stereoisomerism and local chirality'' Kurt Mislow and Jay Siegel J. Am. Chem. Soc.; 1984; 106(11) pp 3319 - 3328; 〕
==Number of stereoisomers==
A molecule can have multiple stereocenters, giving it many stereoisomers. In compounds whose stereoisomerism is due to chiral centers, the total number of hypothetically possible stereoisomers will not exceed 2''n'', where ''n'' is the number of chiral centers. Molecules with symmetry frequently have fewer than the maximum possible number of stereoisomers.
Species having two equivalent chiral centers, exist as three stereoisomers, RR, SS, and RS, the latter being equivalent to SR. The RS/SR stereoisomer is not chiral, but is called a meso compound. Meso compounds do not exhibit chirality due to the presence of an internal mirror plane of symmetry or a center of symmetry in the structure of the molecule in its most symmetric conformation.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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