Representation of Configuration Isomers and Molecular Chirality

The stereochemistry is usually expressed in structure diagrams by wedged and hashed bonds. A wedge indicates that the substituent is in ont of a reference plane and a hashed bond indicates that the substituent is pointing away om the viewer (behind the reference plane). This projection is applied both to tetrahe- 

H COOH HCOC H msleic scid fumeric aad (CIS - 7) (tram - ) 

Ring systems can also be differentiated into cis/trans arrangements of substituents. 

If the tctravalcnt carbon atom has three difFcrcnt substituents, the molecule is chiral and it is not possible to superimpose it onto its mirror image. Our feet are also chiral objects the right foot is a mirror image of the left one and does not ftt into the left shoe. 

The stereochemical analysis of chiral structures starts with the identification of stereogenic units [101], Those units consist of an atom or a skeleton with distinct ligands. By permutation of the ligands, stcrcoisomcric structures arc obtained. The three basic stereogenic units arc a center of chirality (c.g., a chiral tctravalcnt 

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