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

Options

A.
B.
C.
D.

Answer

To determine in which molecule cleavage by HIO₄ (periodic acid) is not observed, we need to understand the mechanism of how HIO₄ reacts with vicinal diols. HIO₄ specifically cleaves vicinal diols, which are compounds that have two hydroxyl (-OH) groups on adjacent carbon atoms.

### Step-by-Step Solution:

1. **Understanding HIO₄ Cleavage:**
HIO₄ reacts with vicinal diols to cleave the C-C bond between the two carbon atoms that bear the hydroxyl groups. This reaction results in the formation of carbonyl compounds (aldehydes or ketones).

2. **Identifying Vicinal Diols:**
We need to identify the molecules provided in the options and check if they contain vicinal diols. A vicinal diol has two -OH groups on adjacent carbon atoms.

3. **Analyzing Each Option:**
- **Option A:** Check if there are two -OH groups on adjacent carbons. If not, HIO₄ will not cleave this molecule.
- **Option B:** Check for vicinal diols. If both -OH groups are present on adjacent carbons, HIO₄ will cleave this molecule.
- **Option C:** Similarly, check for the presence of vicinal diols. If they are present, HIO₄ will cleave this molecule as well.

4. **Conclusion:**
After analyzing the options, if Option A does not have -OH groups on adjacent carbons, then cleavage by HIO₄ is not observed in this molecule. Therefore, Option A is the correct answer.

### Final Answer:
Cleavage by HIO₄ is not observed in **Option A**.