Cahn-Ingold-Prelog method

The absolute configuration at sulfur is specified by the Cahn-Ingold-Prelog method with the provision that the unshared electron pah is considered to be the lowest ranking substituent. 

When a molecule has two stereogenic centers, each has its own configuration and can be classified (R) or (5) by the Cahn-Ingold-Prelog method. There are a total of four isomers, since the first center may be (R) or (5) and so may the second. Since a molecule can have only one mirror image, only one of the other three can be the enantiomer of A. This is B [the mirror image of an (R) center is always an (5) center). The compounds C and D are a second pair of enantiomers and the rela-... 

CIP (Cahn, Ingold, Prelog) method, CIP system The CIP sequencing rules establish the conventional ordering of ligands for the unambiguous description of absolute configuration by descriptors such as R, S P, M E, Z. 

Solution This problem deals with configuration, the arrangement of atoms that characterizes a particular stereoisomer. One method of assigning configuration, called the Cahn-Ingold-Prelog Method, is by use of the prefixes R and S. Two steps are involved in this process ... 

Cahn-Ingold-Prelog Method FOR Determining Priority OF Attached Groups... 

Figure 2.11 Using the Cahn-Ingold-Prelog method to assign absolute configuration at a chiral center.

This method is useful for portraying chemical formulae in typescripts and manuscripts, as a lot of information is conveyed in a condensed manner. However, it suffers from the problem that it does not give a pictorial representation of the stereochemistry of the molecule. In order to overcome this deficiency, it is possible to include the appropriate Cahn-Ingold-Prelog prefix, namely R or S, to indicate diastereo details, or one of the cis, trans, ortho, meta or para prefixes to indicate geometrical details. ... 

In order to describe the absolute configuration of chiral allenes, the Cahn-Ingold-Prelog (CIP) rules are first used to ascertain the priorities at the each terminal carbon, as is done for alkenes at this point the similarity with alkenes ends. The method will be demonstrated with the trisubstituted allene 14a ... 

Since its introduction in 1956, the Cahn-Ingold-Prelog system has become the standard method of stereochemical notation. 

The Cahn-Ingold-Prelog system is the standard method of stereochemical notation. It replaced an older system based on analogies to specified reference compounds that used the prefixes d and l, a system that is still used for carbohydrates and amino acids. We will use d and l notation when we get to Chapters 23-26, but won t need it until then. 

Cahn-Ingold-Prelog convention The accepted method for designating the absolute configuration of a chirality center (usually an asymmetric carbon) as either (/ ) or (S). (p. 175) chiral Different from its mirror image, (p. 168)... 

---