Question

Identify the number of stereoisomers for the compound 2,3-dichlorobutane, and draw their structures including R/S configurations for each chiral center present in the compound.

Answer 1

2,3-dichlorobutane has two chiral centers, which are carbons 2 and 3. Therefore, there are 2^n possible stereoisomers, where n is the number of chiral centers. In this case, n=2, so there are 2^2 = 4 possible stereoisomers. These stereoisomers are:1.  2R,3R -2,3-dichlorobutaneStructure: H3C-CHCl-CHCl-CH3Chiral centers: C2  R  and C3  R 2.  2S,3S -2,3-dichlorobutaneStructure: H3C-CHCl-CHCl-CH3Chiral centers: C2  S  and C3  S 3.  2R,3S -2,3-dichlorobutaneStructure: H3C-CHCl-CHCl-CH3Chiral centers: C2  R  and C3  S 4.  2S,3R -2,3-dichlorobutaneStructure: H3C-CHCl-CHCl-CH3Chiral centers: C2  S  and C3  R These four stereoisomers include two pairs of enantiomers:  2R,3R  and  2S,3S , and  2R,3S  and  2S,3R .