Isomers chirality

Naturally occurring compounds are usually single enantiomers, e.g. L-morphine, L-hyoscine. Atropine is an exception. Although synthesised in the belladonna plant as L-atropine, it is partly converted in the extraction process to the D isomer (chiral inversion), and is administered as a racemic mixture. During this process its OCHF,... 

The single most important physical property that differentiates enantiomers is their ability to rotate the plane of plane polarized light. This property is called optical activity and is displayed only by chiral molecules. Thus, stereoisomers which are also chiral are known as optical isomers. Chiral molecules that rotate polarized light in a clockwise fashion are termed dextrorotatory (d) while those that rotate the beam counterclockwise are levorotatory (/). Enantiomers have optical rotations of die same magnitude but of different signs (d or /). 

Geometrical isomers are not necessarily optical isomers. For instance, the trans isomer of [Co(en)2Cl2]+ shown in Fig. 20.17 is identical to its mirror image. Since this isomer is superimposable on its mirror image, it does not exhibit optical isomerism and is therefore not chiral. On the other hand, cis-[Co(en)2Cl2]+ is not superimposable on its mirror image thus a pair of enantiomers exists for the complex ion, making the cis isomer chiral. 

Stereoisomers include cis and trans isomers, chiral isomers, compounds with different conformations of chelate rings, and other isomers that differ only in the geometry of attachment to the metal ion. As mentioned at the beginning of this chapter, study of stereoisomers provided much of the experimental evidence used by Werner to develop and defend his coordination theory. Similar study of new compounds is useful in establishing structures and reactions, even though development of experimental methods such as automated X-ray diffraction can shorten the process considerably. 

Enantiomers - two isomers which are mirror images of each other also known as optical isomers. Chirality is (yet) another term for enantiomerism. 

II. Nerve Agent Stereo-Isomers Chiral Analysis.98... 

II. NERVE AGENT STEREO-ISOMERS CHIRAL ANALYSIS... 

Vincent, J.B., D.M. Kirby, T.V. Nguyen, and G. Vigh. 1997b. A family of single-isomer chiral resolving agents for capillary electrophoresis. 2. Hepta-6-sulfato-P-cyclo-dextrin. Anal. Chem. 69 4419-4428. 

Additionally, LC-MS is the method of choice for the separation and detection of chiral impurities in pharmaceuticals. The analysis of chiral impurities in pharmaceuticals is of importance because the D-isomer of a dmg can have a different pharmacological, metabolic, and toxicological activity from the L-isomer. Chiral impurities of amino acids, present in peptide drugs, have been separated and determined by LC-MS. The selectivity of MS detection eliminated interference from other peaks that appeared when a UV detector was used for detection. 

Electrophoretic and chromatographic separations conducted on microchips are often fast therefore, they do not lower the temporal resolution of the whole analytical process as much as most conventional hyphenated systems (see Chapter 6). Although microscale separations are not always expected to present as good resolution as the conventional ones, they can often contribute to the selectivity of the analytical process. For example, MS cannot directly be used to distinguish ions of optical isomers. Chiral separations can be carried... 

Ji5)-PhCHMeNH3 CIO4 in favour of the 5-isomer. Chiral macrocyclic diamines... 

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