Absolute configuration

Absolute configuration specifies the three-dimensional arrangement of atoms around a stereogenic center independently of other molecules, commonly using the R/S convention.

Cahn–Ingold–Prelog priority rules: A rule system that ranks substituents attached to a stereogenic center by atomic number and successive tie-breakers. These rules assign priorities before the center receives an R or S designation.
Chirality: The property of an object that makes it non-superimposable on its mirror image. Absolute configuration gives a precise description of molecular handedness.
IUPAC nomenclature: The standardized system for naming chemical substances according to rules established by the International Union of Pure and Applied Chemistry. Systematic names can include R/S descriptors to distinguish stereoisomers.
Relative configuration: The spatial relationship between stereogenic centers in a molecule or between a molecule and a reference compound. Unlike absolute configuration, it describes arrangements by comparison with a reference.
R/S notation: A system that labels a stereogenic center R or S according to the ordered arrangement of its substituents. It is the standard notation used to express absolute configuration.
Stereochemistry: The study of the three-dimensional arrangement of atoms in molecules and how that arrangement affects properties and reactions. Absolute configuration is one part of stereochemical description.
Thalidomide: A pharmaceutical compound whose enantiomers interconvert under physiological conditions and whose history exposed severe risks in pregnancy. Its stereochemistry illustrates why an R/S label alone does not ensure a stable, isolated enantiomer.
Optical rotation: The measured rotation of plane-polarized light as it passes through an optically active material. Its positive or negative sign cannot be inferred from an R or S designation.
Stereogenic center: An atom at which exchanging two attached groups produces a stereoisomer. A common site whose atom arrangement is described by an R or S label.
Enantiomer: One of a pair of stereoisomers that are non-superimposable mirror images. Enantiomers have opposite configurations at every corresponding stereogenic center.

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