Do you have any references on the graphical representation of stereochemical configuration?
Here are a few different references:
II. Cahn-Ingold-Prelog (CIP) priority rules:
1. ^ Robert Sidney Cahn; Christopher Kelk Ingold; Vladimir Prelog (1966). "Specification of Molecular Chirality". Angewandte Chemie International Edition 5 (4): 385-415. doi:10.1002/anie.196603851.
2. ^ Vladimir Prelog; Günter Helmchen (1982). "Basic Principles of the CIP-System and Proposals for a Revision". Angewandte Chemie International Edition 21 (8): 567-583. doi:10.1002/anie.198205671.
III. From our manual:
Absolute stereochemistry is calculated for tetrahedral atoms and double bonds according to the Cahn-Ingold-Prelog (CIP) priority rules. The CIP rules are designed to order ligands by their priority and determine a descriptor based on the orientation of the ordered ligands in space. A ligand is an entity attached to a stereocenter. For example, a tetrahedral carbon has four ligands corresponding to its four substituents. When a tetrahedral carbon is in a ring, it still has four ligands: the two ligands outside the ring, a third consisting of the ring “unpeeled” clockwise, and a fourth consisting of the ring “unpeeled” counterclockwise.
Five rules used to determine the priority of ligands are summarized below in simplified form. For more detailed information, see the references. They are checked sequentially as follows:
Higher atomic number precedes lower
Higher atomic mass precedes lower
cis precedes trans
Like pairs of descriptors precede unlike pairs
R precedes S
Chem & Bio Draw checks differences up to 15 atoms distant from the stereocenter.
After the ligands are ranked, an indicator is assigned as shown in the following table.
|Double bond||Z if the highest ranking ligand of each pair are on the same side of the bond; otherwise E.|
|Tetrahedral atom||When the lowest-ranking ligand is located behind the central atom: R when remaining 3 ligands are arranged clockwise in descending order S when remaining 3 ligands are arranged counterclockwise in descending order r or s is used for pseudo asymmetric atoms|