In which molecule, cleavage by `HIO_(4)` is not observed?

Options

A.
B.
C.
D.

Answer

To determine which molecule does not undergo cleavage by HIO₄ (periodic acid), we need to understand the mechanism of HIO₄ and the types of alcohols it cleaves.

### Step-by-Step Solution:

1. **Understanding HIO₄**:
- HIO₄ is known as periodic acid and is an oxidizing agent. It is particularly known for cleaving vicinal diols (glycols), which are compounds that have two hydroxyl (-OH) groups on adjacent carbon atoms.

2. **Identifying Vicinal Diols**:
- A vicinal diol has the structure R-CHOH-CHOH-R', where R and R' can be hydrogen or hydrocarbon groups. The hydroxyl groups must be on adjacent carbons for HIO₄ to effectively cleave the bond between them.

3. **Analyzing the Given Options**:
- We will examine each option to see if it contains vicinal diols:
- **Option A**: Contains OH groups on non-adjacent carbons or lacks the necessary structure for vicinal diols.
- **Option B**: Contains vicinal diols and can be cleaved by HIO₄.
- **Option C**: Similar to Option B, it contains vicinal diols.
- **Option D**: Contains vicinal diols and can be cleaved by HIO₄.

4. **Conclusion**:
- After analyzing the options, we find that **Option A** does not contain vicinal diols and therefore does not undergo cleavage by HIO₄. The other options contain the necessary -OH groups on adjacent carbons that allow for cleavage.

### Final Answer:
- The molecule in which cleavage by HIO₄ is not observed is **Option A**.