meso- - определение. Что такое meso-
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Что (кто) такое meso- - определение

MESO
Meso-compound; Meso form; Meso compounds; Meso Compound; Meso Compounds; Meso isomers; Meso isomer; Meso-
  • 4}} symmetry.

Meso-         
·- ·Alt. of Mes-.
meso-         
['m?s??, 'm?z??, 'mi:s??, 'mi:z??]
¦ combining form middle; intermediate: mesomorph.
Origin
from Gk mesos 'middle'.
Meso Gerakari         
VILLAGE IN GREECE
Meso Gerakari, Greece; Meso Gerakarou, Greece
Meso Gerakari () is a village in the municipal unit of Alykes on the island Zakynthos, Greece. According to a 2001 census, Meso Gerakari contained approximately 402 inhabitants.

Википедия

Meso compound

A meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active. This means that despite containing two or more stereocenters, the molecule is not chiral. A meso compound is "superimposable" on its mirror image (not to be confused with superposable, as any two objects can be superposed over one another regardless of whether they are the same). Two objects can be superimposed if all aspects of the objects coincide and it does not produce a "(+)" or "(-)" reading when analyzed with a polarimeter. The name is derived from the Greek mésos meaning “middle”.

For example, tartaric acid can exist as any of three stereoisomers depicted below in a Fischer projection. Of the four colored pictures at the top of the diagram, the first two represent the meso compound (the 2R,3S and 2S,3R isomers are equivalent), followed by the optically active pair of levotartaric acid (L-(R,R)-(+)-tartaric acid) and dextrotartaric acid (D-(S,S)-(-)-tartaric acid). The meso compound is bisected by an internal plane of symmetry that is not present for the non-meso isomers (indicated by an X). That is, on reflecting the meso compound through a mirror plane perpendicular to the screen, the same stereochemistry is obtained; this is not the case for the non-meso tartaric acid, which generates the other enantiomer. The meso compound must not be confused with a 50:50 racemic mixture of the two optically-active compounds, although neither will rotate light in a polarimeter.

It is a requirement for two of the stereocenters in a meso compound to have at least two substituents in common (although having this characteristic does not necessarily mean that the compound is meso). For example, in 2,4-pentanediol, both the second and fourth carbon atoms, which are stereocenters, have all four substituents in common.

Since a meso isomer has a superposable mirror image, a compound with a total of n chiral centers cannot attain the theoretical maximum of 2n stereoisomers if one of the stereoisomers is meso.

A meso isomer need not have a mirror plane. It may have an inversion or a rotoreflexion symmetry such as S4. For example, there are two meso isomers of 1,4-difluoro-2,5-dichlorocyclohexane but neither has a mirror plane, and there are two meso isomers of 1,2,3,4-tetrafluorospiropentane (see figure). In fact, a meso compound may have no symmetry in some conformations, for instance, meso tartaric acid in its gauche conformation. A molecule with no symmetry is chiral. But the presence of equal quantities of the right-handed and left-handed conformations will mean that the mixture will not rotate polarized light.

Примеры употребления для meso-
1. Bermudez said the region is trying to consolidate its efforts under a plan known as the Meso–American Strategy to combat organized crime.
2. "The pre–classic was a complex and sophisticated society, and this is the greatest compilation of murals ever found in Meso–America.
3. Expectant mothers sucking on their bargain–basement cigs outside the maternity ward, pipe–puffing intellectuals, plutocrats drawing on velvety Coronas – they might not know it but all hold pieces of meso–American history in their hands.
4. Archaeologist William Saturno of the University of New Hampshire and Harvard‘s Peabody Museum of Archaeology and Ethnology said yesterday that the San Bartolo site, in Guatemala‘s Peten wilderness, is "the find of a lifetime," depicting the Mayan creation myth and the crowning of a king in vivid color on a plaster wall as though "parts of it . . . were painted yesterday." The painting is the oldest intact mural ever found in Meso–America, dating to about 150 B.C. in the Mayan "pre–classic" period.