Compounds E and F are two isomers of 2,3-dibromopentane drawn in staggered conformations. Which compounds (A–D) in Figure 5.8 are identical to E and F?

The R and S nomenclature is helpful to distinguish between the enantiomers, diastereomers, and identical structures. The R and S are assigned at the chiral centers based on the priority of groups.

The R, S nomenclature decides the relationship between the isomers.

The relationship of E and F isomers with the given images of 5.8 is as below:

R and S nomenclature

• E and A are diastereomers because E has 2R, 3R, and A has 2S, 3R.
• E and B are diastereomers because E has 2R, 3R, and B has 2R, 3S.
• E and C are identical because E has 2R, 3R, and C has 2R, 3R.
• E and D are enantiomers because E has 2R, 3R, and D has 2S, 3S.
• F and A are identical because F has 2S, 3R, and A has 2S, 3R.
• F and B are enantiomers because F has 2S, 3R, and B has 2R, 3S.
• F and C are diastereomers because F has 2S, 3R, and C has 2R, 3R.
• F and D are diastereomers because the F has 2S, 3R, and D has 2S, 3S.

Stereoisomers