Question

Consider the ball-and-stick models of A-D. How is each pair of compounds related: (a) A and B; (b) A and C; (c) A and D; (d) C and D? Choose from identical molecules, enantiomers, or diastereomers.

Short answer

1. A and B are Identical molecules.
2. A and C are enantiomers.
3. A and D are diastereomers.
4. C and D are diastereomers.

Step-by-step solution

Enantiomers and diastereomers

The enantiomers are the stereoisomers of a compound which are non-superimposable mirror images of each other.The compound, which has one stereogenic center, has two enantiomers.

The enantiomers have the same physical properties such as melting points, boiling points, etc.

Diastereomers are the isomers that have entirely different configurations. The physical properties of the diastereomers are different because they are different compounds.

Relationship and the structures of the given compounds

The structures of the given compounds from the ball and stick model, along with their R and S configuration, is shown below:

2(R),3(S), dichloro-1-butanol

A

B

2(R),3(S)-dichloro-1-butanol

C

2(S),3(R)-dichloro-1-butanol

D

2(S),3(S)-dichloro-1-butanol

1. The compounds A and B are identical molecules. Compound A can be converted into compound B by the rotation of the carbon-carbon bond. It will result in the change in the orientation of molecule B, which will become identical to A.
2. The molecules A and C are enantiomers. They are mirror images of each other.
3. The molecules A and D are the diastereomers.
4. The molecules C and D are also the diastereomers.