Which of the following is not cleaved by HI even at 525K ?

Options

A. `C_(6)H_(5)OCH_(3)`
B. `C_(6)H_(5)OC_(6)H_(5)`
C. `C_(6)H_(5)OC_(3)H_(7)`
D.

Answer

To solve the question of which compound is not cleaved by HI even at 525 K, we can follow these steps:

### Step 1: Understand the Cleavage Mechanism of Ethers
Ethers can undergo cleavage when treated with hydrogen iodide (HI). The cleavage typically occurs at the bond between the alkyl group and the oxygen atom. The result of this cleavage is the formation of an alcohol and an alkyl iodide.

**Hint**: Remember that ethers can be symmetrical or unsymmetrical, which affects how they cleave.

### Step 2: Analyze the Types of Ethers
1. **Symmetrical Ethers**: In symmetrical ethers, both alkyl groups are the same (e.g., R-O-R). Cleavage will yield the same alcohol and iodide.

2. **Unsymmetrical Ethers**: In unsymmetrical ethers, the smaller alkyl group tends to form the iodide because it is more favorable for the larger group to remain as an alcohol due to steric hindrance.

**Hint**: Consider how the size of the alkyl groups influences the cleavage products.

### Step 3: Identify Alkyl Aryl Ethers
Alkyl aryl ethers (e.g., C6H5O-R) cleave at the alkyl-oxygen bond. The aryl group (like phenyl, C6H5) is more stable due to resonance, which makes it less likely to undergo cleavage.

**Hint**: Aryl groups stabilize the ether bond, making them less reactive towards cleavage.

### Step 4: Evaluate the Given Options
1. **C6H5OCH3**: Cleaves to C6H5OH and CH3I.
2. **C6H5OC6H5**: Symmetrical ether, cleaves to C6H5OH and C6H5I.
3. **C6H5O-C3H7**: Cleaves to C6H5OH and C3H7I.
4. **Cyclic Ethers**: Cyclic ethers do not undergo cleavage with HI, even at high temperatures like 525 K.

**Hint**: Focus on the structure of cyclic ethers and their stability.

### Step 5: Conclusion
Among the options, cyclic ethers do not undergo cleavage with HI at 525 K. Therefore, the answer to the question is that cyclic ethers are not cleaved by HI.

**Final Answer**: Cyclic ethers are not cleaved by HI even at 525 K.