Fig. 36

Stereoconfiguration examples. A Variants of identical tetrahedral configuration of the same chiral center. a Representations with explicit hydrogen atom using: (i) two bonds in, one behind and one in front of the drawing plane (favored representation); (ii) one bond in, two in front of and one behind the drawing plane; (iii) one bond in, one bond in front of and two bonds behind the drawing plane; (iv and v) two bonds in front of and two bond behind the drawing plane. b Equivalent representations of the same configuration with implicit hydrogen atom if possible. B Representation of a double bond with unknown cis/trans configuration as represented in PubChem (i) and corresponding accepted IUPAC recommendations (ii–iii)