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Le Bel-van't Hoff rule states that for a structure with n asymmetric carbon atoms, there is a maximum of 2 n different stereoisomers possible. As an example, D-glucose is an aldohexose and has the formula C 6 H 12 O 6. Four of its six carbon atoms are stereogenic, which means D-glucose is one of 2 4 =16 possible stereoisomers. [20] [21]
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 2 4 = 16 stereoisomers. This is indeed the case: these chemicals are two enantiomers each of eight different diastereomers : allose , altrose , glucose , mannose , gulose , idose , galactose ...
A molecule having multiple stereocenters will produce many possible stereoisomers. In compounds whose stereoisomerism is due to tetrahedral (sp 3) stereogenic centers, the total number of hypothetically possible stereoisomers will not exceed 2 n, where n is the number of tetrahedral stereocenters. However, this is an upper bound because ...
The possibilities for different isomers continue to multiply as more stereocenters are added to a molecule. In general, the number of stereoisomers of a molecule can be determined by calculating 2 n, where n = the number of chiral centers in the molecule. This holds true except in cases where the molecule has meso forms.
A molecule may contain any number of stereocenters and any number of double bonds, and each usually gives rise to two possible isomers. A molecule with an integer n describing the number of stereocenters will usually have 2 n stereoisomers, and 2 n−1 diastereomers each having an associated pair of enantiomers.
Knowing the number of asymmetric carbon atoms, one can calculate the maximum possible number of stereoisomers for any given molecule as follows: . If n is the number of asymmetric carbon atoms then the maximum number of isomers = 2 n (Le Bel-van't Hoff rule)
Of the three stereoisomers, two are enantiomers (levo- and dextro-2,3-butanediol) and one is a meso compound. [ 1 ] [ 2 ] The enantiomeric pair have (2 R , 3 R ) and (2 S , 3 S ) configurations at carbons 2 and 3, while the meso compound has configuration (2 R , 3 S ) or, equivalently, (2 S , 3 R ).
Stereochemistry, a subdiscipline of chemistry, studies the spatial arrangement of atoms that form the structure of molecules and their manipulation. [1] The study of stereochemistry focuses on the relationships between stereoisomers, which are defined as having the same molecular formula and sequence of bonded atoms (constitution) but differing in the geometric positioning of the atoms in space.