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Optical activity is reciprocal, i.e. it is the same for opposite directions of wave propagation through an optically active medium, for example, clockwise polarization rotation from the point of view of an observer.
Louis Pasteur - pioneering stereochemist. Chirality can be traced back to 1812, when physicist Jean-Baptiste Biot found out about a phenomenon called "optical activity." [10] Louis Pasteur, a famous student of Biot's, made a series of observations that led him to suggest that the optical activity of some substances is caused by their molecular asymmetry, which makes nonsuperimposable mirror ...
It is an important tool in the production of optically active compounds, including drugs. [3] Another term with the same meaning is optical resolution . The use of chiral resolution to obtain enantiomerically pure compounds has the disadvantage of necessarily discarding at least half of the starting racemic mixture.
Different enantiomers or diastereomers of a compound were formerly called optical isomers due to their different optical properties. [29] At one time, chirality was thought to be restricted to organic chemistry, but this misconception was overthrown by the resolution of a purely inorganic compound, a cobalt complex called hexol , by Alfred ...
Specific rotation is an intensive property, distinguishing it from the more general phenomenon of optical rotation. As such, the observed rotation (α) of a sample of a compound can be used to quantify the enantiomeric excess of that compound, provided that the specific rotation ([α]) for the enantiopure compound is known.
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. An optically active compound shows two forms: D-(+) form and L-(−) form.
Two examples of atropisomer synthesis. Axially chiral biaryl compounds are prepared by coupling reactions, e.g., Ullmann coupling, Suzuki–Miyaura reaction, or palladium-catalyzed arylation of arenes. [13] Subsequent to the synthesis, the racemic biaryl is resolved by classical methods.
Macroscopic examples of chirality are found in the plant kingdom, the animal kingdom and all other groups of organisms. A simple example is the coiling direction of any climber plant, which can grow to form either a left- or right-handed helix. In anatomy, chirality is found in the imperfect mirror image symmetry of many kinds of animal bodies.