View source for Chemistry:Le Bel–Van 't Hoff rule

In [[Chemistry:Organic chemistry|organic chemistry]], the '''Le Bel–Van&nbsp;'t Hoff rule''' states that the number of stereoisomers of an organic compound containing no internal planes of symmetry is 2<sup>''n''</sup>, where ''n'' represents the number of [[Chemistry:Asymmetric carbon|asymmetric carbon]] atoms. Joseph Achille Le Bel<ref>{{cite journal |last= Le Bel |first= Joseph Achille |year= 1874 |url= https://babel.hathitrust.org/cgi/pt?id=hvd.hc1j13;view=1up;seq=345 |title= Sur les relations qui existent entre les formules atomiques des corps organiques et le pouvoir rotatoire de leurs dissolutions |language= fr |trans-title= On the relations that exist between the atomic formulas of organic substances and the rotatory power of their solutions |journal= Bulletin de la Société Chimique de Paris |volume= 22 |pages= 337–347 }}</ref> and [[Biography:Jacobus Henricus van 't Hoff|Jacobus Henricus van&nbsp;'t Hoff]]<ref>{{cite journal |last= Van 't Hoff |first= Jacobus Henricus |year= 1874 |url= https://babel.hathitrust.org/cgi/pt?id=hvd.32044106337231;view=1up;seq=479 |title= Sur les formules de structure dans l'espace |language= fr |trans-title= On structural formulas in space |journal= Archives Néerlandaises des Sciences Exactes et Naturelles |volume= 9 |pages= 445–454 }}</ref> both announced this hypothesis in 1874 and that this accounted for all molecular asymmetry known at the time.<ref>{{cite web|title=Le Bel–van 't Hoff rule|url=http://medical-dictionary.thefreedictionary.com/Le+Bel-van't+Hoff+rule|publisher=TheFreeDictionary's Medical dictionary}}</ref>

As an example, four of the carbon atoms of the [[Chemistry:Aldohexose|aldohexose]] class of molecules are asymmetric, therefore the Le Bel–Van&nbsp;'t Hoff rule gives a calculation of 2<sup>4</sup>&nbsp;=&nbsp;16 stereoisomers. This is indeed the case: these chemicals are two [[Chemistry:Enantiomer|enantiomer]]s each of eight different diastereomers: [[Chemistry:Allose|allose]], [[Chemistry:Altrose|altrose]], [[Chemistry:Glucose|glucose]], [[Chemistry:Mannose|mannose]], [[Chemistry:Gulose|gulose]], [[Chemistry:Idose|idose]], [[Chemistry:Galactose|galactose]], and [[Chemistry:Talose|talose]].

:[[File:Aldolhexose stereo.svg|frame|left|Four asymmetric carbon atoms in glucose (the four carbon–oxygen bonds marked in red)]]
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==References==
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[[Category:Stereochemistry]]



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