Which of the following reagents would distinguish ciscyclopenta `-1,2-`diol from the trans-isomer?

Options

A. Aluminium isopropoxide
B. Acetone
C. Ozone
D. `MnO_(2)`

Answer

To distinguish between cis-cyclopenta-1,2-diol and trans-cyclopenta-1,2-diol, we can analyze the properties of the two isomers and the reagents provided. Here’s a step-by-step solution:

### Step 1: Understand the Structures of the Isomers
- **Cis-cyclopenta-1,2-diol** has both hydroxyl (OH) groups on the same side of the cyclopentane ring.
- **Trans-cyclopenta-1,2-diol** has the hydroxyl groups on opposite sides of the ring.

### Step 2: Identify the Reagents
The question provides four reagents:
1. Aluminium isopropoxide
2. Acetone
3. Ozone
4. MnO2

### Step 3: Analyze Each Reagent
1. **Aluminium Isopropoxide**: This reagent oxidizes secondary alcohols to ketones. Since both isomers are secondary alcohols, it will oxidize both to the same ketone, thus cannot distinguish between them.

2. **Acetone**: When treated with diols, acetone can form acetals. For acetal formation, the hydroxyl groups must be on the same side. In the case of cis-cyclopenta-1,2-diol, acetal formation is possible, while for trans-cyclopenta-1,2-diol, it is not. Thus, this reagent can distinguish between the two isomers.

3. **Ozone**: Ozone will oxidize both isomers, breaking any double bonds and forming aldehydes or ketones. Since both isomers will undergo similar oxidation, this reagent cannot distinguish between them.

4. **MnO2**: Like ozone, MnO2 is an oxidizing agent that will convert both isomers into ketones. Therefore, it cannot distinguish between the two isomers.

### Step 4: Conclusion
The only reagent that can distinguish between cis-cyclopenta-1,2-diol and trans-cyclopenta-1,2-diol is **acetone**. The cis isomer can form an acetal, while the trans isomer cannot.

### Final Answer
**B. Acetone** is the reagent that distinguishes cis-cyclopenta-1,2-diol from trans-cyclopenta-1,2-diol.

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