Given two molecules, $(2R,3R)-2,3-\mathrm{dibromobutane}$ and $(2R,3S)-2,3-\mathrm{dibromobutane}$, which of the following is a diastereomer of $(2R,3R)-2,3-\mathrm{dibromobutane}$?

• A. $(2R,3S)-2,3-\mathrm{dibromobutane}$
• B. $(2S,3R)-2,3-\mathrm{dibromobutane}$
• C. $(2R,3R)-2,3-\mathrm{dibromobutane}$
• D. $(2S,3S)-2,3-\mathrm{dibromobutane}$

Answer: (B)

Verified step by step guidance

1. Identify the stereocenters in the molecule. Here, 2,3-dibromobutane has two chiral centers at carbons 2 and 3, each of which can be R or S configuration.
2. Recall the definitions: Enantiomers are non-superimposable mirror images differing at all chiral centers, while diastereomers differ at one or more (but not all) chiral centers and are not mirror images.
3. Given the molecule (2R,3R)-2,3-dibromobutane, compare it to the other options by checking the configuration at each chiral center.
4. Determine which molecule differs in configuration at only one chiral center (either carbon 2 or carbon 3) compared to (2R,3R). This molecule will be a diastereomer.
5. Exclude the molecule that differs at both centers (which would be the enantiomer) and the molecule that is identical (same configuration), leaving the one that differs at only one center as the diastereomer.