Which of following reagents does not give isobutane when reacted with isobutyl magnesium bromide?

Options

A. `CH_(3)-C-=CH`
B. `CH_(3)-overset(O)overset(||)C-CH_(2)-overset(O)overset(||)C-O-CH_(3)`
C. `CH_(3)-CH_(2)-OH`
D. `PhOCH_(3)`

Answer

To solve the question of which reagent does not give isobutane when reacted with isobutyl magnesium bromide, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Grignard Reagent**:
- The reagent in question is isobutyl magnesium bromide (C4H9MgBr). This is a Grignard reagent which is known for its nucleophilic properties.

2. **Understand the Reaction**:
- Grignard reagents react with electrophiles to form new carbon-carbon bonds. They can also react with acidic protons to form hydrocarbons.

3. **Determine the Nature of the Reagents**:
- We need to analyze the given reagents to see which one has acidic hydrogen that can react with the Grignard reagent.
- Common reagents that can be tested include alcohols, carboxylic acids, and other compounds that may contain acidic protons.

4. **Evaluate Each Reagent**:
- **Alcohols (e.g., CH3CH2OH)**: These contain an -OH group, which has an acidic hydrogen that can react with the Grignard reagent to form isobutane.
- **Alkynes**: Alkynes have acidic hydrogens due to the sp-hybridized carbon atom. They can also react with Grignard reagents.
- **Phenols (e.g., PHOCH3)**: Phenols have acidic hydrogens and can react with Grignard reagents.
- **Ether (e.g., R-O-R')**: Ethers do not have acidic hydrogens and therefore will not react with Grignard reagents.

5. **Identify the Non-Reactive Reagent**:
- Among the reagents, the ether (PHOCH3) does not have acidic hydrogen and cannot react with isobutyl magnesium bromide to produce isobutane.

### Conclusion:
The reagent that does not give isobutane when reacted with isobutyl magnesium bromide is **PHOCH3 (an ether)**.

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