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There are three common naming conventions for specifying one of the two enantiomers (the absolute configuration) of a given chiral molecule: the R/S system is based on the geometry of the molecule; the (+)- and (−)- system (also written using the obsolete equivalents d- and l-) is based on its optical rotation properties; and the D/L system is based on the molecule's relationship to ...
In a mixture of enantiomers, these methods can help quantify the optical purity by integrating the area under the NMR peak corresponding to each stereoisomer. Accuracy of integration can be improved by inserting a chiral derivatizing agent with a nucleus other than hydrogen or carbon, then reading the heteronuclear NMR spectrum: for example ...
Pure enantiomers also exhibit the phenomenon of optical activity and can be separated only with the use of a chiral agent. In nature, only one enantiomer of most chiral biological compounds, such as amino acids (except glycine, which is achiral), is present. Enantiomers differ by the direction they rotate polarized light: the amount of a chiral ...
Able to differentiate between enantiomers and from the racemate; (+) from (-) and (±) Spectroscopic: Polarimetry: Polarimetry uses the innate property of chiral molecules to rotate the plane-polarized light in equal and opposite direction. This method can be used to distinguish between enantiomers and from the racemate; (+) from (-) and (±)
Ultraviolet–visible spectroscopy (UV–vis) can distinguish between enantiomers by showing a distinct Cotton effect for each isomer. UV–vis spectroscopy sees only chromophores, so other molecules must be prepared for analysis by chemical addition of a chromophore such as anthracene.
If a reaction gave the enantiomer of a known configuration, as indicated by the opposite sign of optical rotation, it would indicate that the absolute configuration is inverted. In 1951, Johannes Martin Bijvoet for the first time used in X-ray crystallography the effect of anomalous dispersion , which is now referred to as resonant scattering ...
Enzymes, which are chiral, often distinguish between the two enantiomers of a chiral substrate. One could imagine an enzyme as having a glove-like cavity that binds a substrate. If this glove is right-handed, then one enantiomer will fit inside and be bound, whereas the other enantiomer will have a poor fit and is unlikely to bind.
This is to give an overview of the evolving chirality nomenclature system commonly employed to distinguish enantiomers of a chiral drug. In the beginning, enantiomers were distinguished based on their ability to rotate the plane of plane-polarized light.