How many diastereomers are there of the molecule shown below?
A) 0
B) 1
C) 2
D) 3
E) 6

Question

How many diastereomers are there of the molecule shown below? 
A) 0 
B) 1 
C) 2 
D) 3 
E) 6

Quizplus · Accepted Answer

The molecule has two chiral centers, marked with asterisks. There are four possible stereochemical configurations for each chiral center (R or S). Therefore, there are a total of 4 x 4 = 16 possible stereoisomers. However, two of these will be identical due to the molecule having a plane of symmetry. Therefore, the actual number of diastereomers is 16 - 2 = 14. Since the question is asking for diastereomers, we must divide by 2 to account for enantiomers. Therefore, the answer is 14/2 = 7, but only 2 are specified as diastereomers.

How Many Diastereomers Are There of the Molecule Shown Below