Chemistry:Le Bel–Van 't Hoff rule

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In organic chemistry, the Le Bel–Van 't Hoff rule states that the number of stereoisomers of an organic compound containing no internal planes of symmetry is 2n, where n represents the number of asymmetric carbon atoms. Joseph Achille Le Bel[1] and Jacobus Henricus van 't Hoff[2] both announced this hypothesis in 1874 and that this accounted for all molecular asymmetry known at the time.[3]

As an example, four of the carbon atoms of the aldohexose class of molecules are asymmetric, therefore the Le Bel–Van 't Hoff rule gives a calculation of 24 = 16 stereoisomers. This is indeed the case: these chemicals are two enantiomers each of eight different diastereomers: allose, altrose, glucose, mannose, gulose, idose, galactose, and talose.

Four asymmetric carbon atoms in glucose (the four carbon–oxygen bonds marked in red)

References