Which of the following pairs are enantiomers?

Options

A.
B.
C.
D.

Answer

To determine which pairs are enantiomers, we need to follow these steps:

### Step 1: Understand Enantiomers
Enantiomers are pairs of molecules that are non-superimposable mirror images of each other. They must have at least one chiral center (a carbon atom bonded to four different groups).

### Step 2: Identify Chiral Centers
For each pair of compounds given in the question, identify if they have chiral centers. A chiral center is typically a carbon atom attached to four different substituents.

### Step 3: Assign Priorities
Using the Cahn-Ingold-Prelog priority rules, assign priorities to the substituents attached to the chiral centers:
1. The higher the atomic number of the atom directly attached to the chiral carbon, the higher the priority.
2. If two substituents have the same atom, move to the next atom in the chain until a difference is found.

### Step 4: Determine Configuration
Determine the configuration (R or S) of each chiral center:
- If the order of the substituents from highest to lowest priority is clockwise, it is designated as R.
- If it is counterclockwise, it is designated as S.
- If the lowest priority group is in the vertical position (away from you), the configuration remains as determined. If it is in the horizontal position (towards you), the configuration is inverted.

### Step 5: Compare the Configurations
For each pair of compounds:
- If one compound is R and the other is S at the same chiral center, they are enantiomers.
- If both compounds have the same configuration (both R or both S), they are not enantiomers.

### Step 6: Conclusion
After analyzing the pairs, identify which pairs are enantiomers based on the configurations determined in the previous step.

### Example Solution:
Assuming we have pairs A, B, C, and D:
- Pair A: Chiral centers identified, configurations assigned (R/S).
- Pair B: Chiral centers identified, configurations assigned (R/S).
- Pair C: Chiral centers identified, configurations assigned (R/S).
- Pair D: Chiral centers identified, configurations assigned (R/S).

After comparing, we find that pairs B and D are enantiomers.

### Final Answer:
The pairs that are enantiomers are those identified in the analysis, specifically option D as per the video transcript.

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