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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 ...
[2] [3] Stereocenters can exist on chiral or achiral molecules; stereocenters can contain single bonds or double bonds. [1] The number of hypothetical stereoisomers can be predicted by using 2 n, with n being the number of tetrahedral stereocenters; however, exceptions such as meso compounds can reduce the prediction to below the expected 2 n. [4]
If two molecules with more than one chiral centre differ in one or more (but not all) centres, they are diastereomers. All stereoisomers that are not enantiomers are diastereomers. Diastereomerism also exists in alkenes. Alkenes are designated Z or E depending on group priority on adjacent carbon atoms. E/Z notation describes the absolute ...
Compare the atomic number (Z) of the atoms directly attached to the stereocenter; the group having the atom of higher atomic number Z receives higher priority (i.e. number 1). If there is a tie, the atoms at distance 2 from the stereocenter have to be considered: a list is made for each group of further atoms bonded to the one directly attached ...
If the two bonds on each carbon connect to different atoms, two distinct conformations are possible, that differ from each other by a twist of 180 degrees of one of the carbons about the double bond. The classical example is dichloroethene C 2 H 2 Cl 2 {\displaystyle {\ce {C2H2Cl2}}} , specifically the structural isomer Cl − HC = CH − Cl ...
Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two. Diastereomers differ from enantiomers in that the latter are pairs of stereoisomers that differ in all stereocenters and are therefore mirror images of one another. [3]
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.