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A chiral substance is enantioenriched or heterochiral when its enantiomeric ratio is greater than 50:50 but less than 100:0. [23] Enantiomeric excess or e.e. is the difference between how much of one enantiomer is present compared to the other.
A molecule having exactly one chiral stereocenter (usually an asymmetric carbon atom) can be labeled (R) or (S), but a molecule having multiple stereocenters needs more than one label. For example, the essential amino acid L -threonine contains two chiral stereocenters and is written (2 S ,3 S )-threonine.
Stereochemistry, a subdiscipline of chemistry, studies the spatial arrangement of atoms that form the structure of molecules and their manipulation. [1] The study of stereochemistry focuses on the relationships between stereoisomers, which are defined as having the same molecular formula and sequence of bonded atoms (constitution) but differing in the geometric positioning of the atoms in space.
This means that although all chirality centers are stereocenters, not every stereocenter is a chirality center. Stereocenters are important identifiers for chiral or achiral molecules. As a general rule, if a molecule has no stereocenters, it is considered achiral. If it has at least one stereocenter, the molecule has the potential for chirality.
[4] [5] The configuration of other chiral compounds was then related to that of (+)-glyceraldehyde by sequences of chemical reactions. For example, oxidation of (+)-glyceraldehyde (1) with mercury oxide gives (−)-glyceric acid (2), a reaction that does not alter the stereocenter. Thus the absolute configuration of (−)-glyceric acid must be ...
Chiral purity is a measure of the purity of a chiral drug. Other synonyms employed include enantiomeric excess , enantiomer purity, enantiomeric purity, and optical purity. Optical purity is an obsolete term since today most of the chiral purity measurements are done using chromatographic techniques (not based on optical principles).
Chirality (/ k aɪ ˈ r æ l ɪ t i /) is a property of asymmetry important in several branches of science. The word chirality is derived from the Greek χείρ (kheir), "hand", a familiar chiral object. An object or a system is chiral if it is distinguishable from its mirror image; that is, it cannot be superposed (not to be confused with ...
Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.