Meso compound

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A meso compound or meso isomer is a chemical compound whose molecules contain 2 or more asymmetric atoms (stereocenters) but is optically inactive (or achiral). In another definition a meso compound is an optically inactive member of a set of stereoisomers, at least two of which are optically active ^[1].

For example, one of the isomers of tartaric acid depicted below is a meso compound. An internal mirror plane exists bisecting the molecule; on rotating the molecule 180° on a plane perpendicular to the screen (that is, superposing the bottom OH with the top one), the same apparent stereochemistry is obtained. (see Fischer projection)

For a compound with multiple asymmetric carbons, the presence of an internal plane of symmetry indicates that the compound is achiral. The cis isomer of cyclooctene is also considered a meso compound. The trans form can be resolved into an enantiomeric pair.

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v • d • e Concepts in asymmetric synthesis Nomenclature Chirality, Stereocenter, Stereoisomer, Enantiomer, Diastereomer, Meso compound, Planar chirality, Chiral ligand, Axial chirality Analysis Optical rotation, Enantiomeric excess, Diastereomeric excess, Chiral derivitizing agents Chiral resolution Crystallization, Kinetic resolution, Chiral column chromatography Reactions Asymmetric induction, Chiral pool synthesis, Chiral auxiliaries, Asymmetric catalytic reduction, Asymmetric catalytic oxidation, Organocatalysis, Biocatalysis