Which of the following are not resolvable?

Options

A. `2,3-` Pentadiene
B.
C.
D.

Explanation

To determine which of the given compounds are not resolvable, we need to identify which of them are optically inactive. A compound is optically inactive if it is achiral, meaning it does not have a non-superimposable mirror image. Here’s a step-by-step analysis of the options provided:

### Step 1: Understand the concept of chirality and resolvability
- **Chirality**: A molecule is chiral if it has a non-superimposable mirror image. Chiral molecules can rotate plane-polarized light and are considered optically active.
- **Achirality**: A molecule is achiral if it is superimposable on its mirror image, meaning it does not rotate plane-polarized light and is considered optically inactive.

### Step 2: Analyze each option

**Option A: 2,3-pentadiene**
- Structure: This compound has a double bond and can exist in different configurations.
- Analysis: 2,3-pentadiene can have different substituents on the double bond, making it potentially chiral. However, if the substituents are the same, it can be achiral. In general, 2,3-pentadiene is resolvable when the substituents are different.
- Conclusion: This option is resolvable.

**Option B: Another compound (not specified)**
- Analysis: Without the specific structure, we assume it is a complex molecule that does not exhibit symmetry or identical groups.
- Conclusion: This option is likely optically active and resolvable.

**Option C: Identical compounds**
- Analysis: If the compounds are identical, they cannot have different configurations and thus do not exhibit chirality.
- Conclusion: This option is not resolvable.

**Option D: Compound with a center of symmetry**
- Analysis: A center of symmetry means that for every atom in the molecule, there is an equivalent atom at an equal distance on the opposite side. This leads to achirality.
- Conclusion: This option is not resolvable.

### Final Conclusion
Based on the analysis:
- **Not resolvable options**: C and D.
- **Resolving option**: A and B.

Thus, the correct answer for the question "Which of the following are not resolvable?" is **C and D**.