All GRE Subject Test: Chemistry Resources
Example Question #1 : Diastereomers
A molecule has three chiral centers. How many stereoisomers of this compound will have different boiling points compared to the original molecule?
The first step is to determine how many stereoisomers there are for this molecule. Since the number of stereoisomers is dependent on the number of chiral carbons, we can solve according to the equation , where is the number of chiral centers. Since there are three chiral centers, we determine that there are eight stereoisomers for this molecule. Keep in mind that this number includes the original molecule.
Next, we need to compare the different stereoisomers to the original molecule. The original molecule will have one enantiomer and six diastereomers. Remember that enantiomers have the same physical properties, so we will not include this isomer in the final answer. Diastereomers, on the other hand, have different physical properties compared to the original molecule. As a result, six stereoisomers will have different boiling points compared to the original molecule.