Nomenclature for Dissymmetric and other Chiral Molecules

Although tetrahedral carbon is probably the most important and certainly the most common chiral structure, many other chiral molecular structures can be classified as asymmetric or dissymmetric. In the very late nineteenth century, the father of coordination chemistry Professor Alfred Werner of the University of Zurich developed a theory for the structure of compounds where a central atom other than carbon could form bonds to different numbers of atoms. This coordination theory was most successful and applicable to structures in which the number of bonds (the coordination number) was 6. Werner was very familiar with the work of van t Hoff and Le Bel on tetrahedral carbon, and he spent many years trying to synthesize and separate compounds that were based on octahedral geometry. 

FIGURE 1.15. The six possible isomers of octahedral MA2B2C2-The lop two isomers are chiral. 

The CIP nomenclature has been applied to virtually all chiral molecules, such that chemists are able to communicate to each other the absolute structure of such species in an unambiguous 

FIGURE 1.17. Nomenclature for helices (a) left-handed hehx, M or A (b) right-handed hehx, P or A. 

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