View source for Chemistry:Klyne–Prelog system

In [[Chemistry:Stereochemistry|stereochemistry]], the '''Klyne–Prelog system''' (named for [[Biography:William Klyne|William Klyne]] and [[Biography:Vladimir Prelog|Vladimir Prelog]]) for describing [[Chemistry:Conformational isomerism|conformations]] about a [[Chemistry:Single bond|single bond]] offers a more systematic means to unambiguously name complex structures, where the torsional or dihedral angles are not found to occur in 60° increments.<ref>Klyne, W & Prelog V. Description of steric relationships across single bonds. ''Experientia'' 16:521–523, 1960.</ref> Klyne notation views the placement of the [[Chemistry:Substituent|substituent]] on the front atom as being in regions of space called anti/syn and clinal/periplanar relative to a reference group on the rear atom. A plus (+) or minus (−) sign is placed at the front to indicate the sign of the dihedral angle. Anti or syn indicates the substituents are on opposite sides or the same side, respectively. Clinal substituents are found within 30° of either side of a dihedral angle of 60° (from 30° to 90°), 120° (90°–150°), 240° (210°–270°), or 300° (270°–330°). Periplanar substituents are found within 30° of either 0° (330°–30°) or 180° (150°–210°). Juxtaposing the designations produces the following terms for the conformers of [[Chemistry:Butane|butane]] (see [[Chemistry:Alkane stereochemistry|Alkane stereochemistry]] for an explanation of conformation nomenclature): gauche butane is ''syn-clinal'' (''+sc'' or ''−sc'', depending on the [[Chemistry:Enantiomer|enantiomer]]), anti butane is ''anti-periplanar'', and eclipsed butane is ''syn-periplanar''.<ref>For textbook discussions of the Klyne–Prelog system, see:
* Anslyn, Eric V. and Dougherty, Dennis A. ''Modern Physical Organic Chemistry''. (2005).
* Carroll, Felix. ''Perspectives on Structure and Mechanism in Organic Chemistry''. (2e, 2010).</ref>

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