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A meso compound or meso isomer is an optically inactive isomer in a set ... For example, there are two meso isomers of 1,4-difluoro-2,5-dichlorocyclohexane but ...
Mesoionic compounds are a subclass of betaines. [1] Examples are sydnones and sydnone imines (e.g. the stimulant mesocarb ), münchnones , [ 1 ] [ 2 ] and mesoionic carbenes . The formal positive charge is associated with the ring atoms and the formal negative charge is associated either with ring atoms or an exocyclic nitrogen or other atom. [ 3 ]
An example of m diads in a polypropylene molecule. ... the diad is called an m diad (formerly meso diad, as in a meso compound, now proscribed [3]).
These include meso compounds, cis–trans isomers, E-Z isomers, and non-enantiomeric optical isomers. Diastereomers seldom have the same physical properties. In the example shown below, the meso form of tartaric acid forms a diastereomeric pair with both levo- and dextro-tartaric acids, which form an enantiomeric pair.
However, compounds that contain an even number of asymmetric atoms sometimes lack chirality because they are arranged in mirror-symmetric pairs, and are known as meso compounds. For instance, meso tartaric acid (shown on the right) has two asymmetric carbon atoms, but it does not exhibit enantiomerism because there is a mirror symmetry plane.
A meso compound is superposable on its mirror image, therefore it reduces the number of stereoisomers predicted by the 2 n rule. This occurs because the molecule obtains a plane of symmetry that causes the molecule to rotate around the central carbon–carbon bond. [12] One example is meso-tartaric acid, in which (R,S) is the same as the (S,R) form
The achiral meso compound (1R,2S)-1,2-diphenyloxirane arises from cis-stilbene, though peroxide epoxidations of the cis-isomer produce both cis- and trans-epoxide products. For example, using tert-butyl hydroperoxide, oxidation of cis-stilbene produces 0.8% cis-stilbene oxide, 13.5% trans-stilbene oxide, and 6.1% benzaldehyde.
This page was last edited on 11 March 2008, at 05:46 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may ...