Which of the following compounds liberate methane when treated with excess of methyl magnesium iodide in dry ether -
(a) `CH_(3)–CH_(2)–CH_(2)OH (b) H_(3)C–CH_(2)–C-=CH`
(c) `H_(3)C–CH_(2)–CO_(2)H` (d) `H_(3)C–CH_(2)–CHO`

Options

A. a, b
B. b, c
C. a, b, c
D. All above

Answer

To determine which of the given compounds liberate methane when treated with excess methyl magnesium iodide (a Grignard reagent) in dry ether, we will analyze each compound step by step.

### Step 1: Understanding Grignard Reagents
Grignard reagents, such as methyl magnesium iodide (CH₃MgI), are nucleophiles and can react with compounds that have acidic protons (H⁺) to liberate methane (CH₄).

### Step 2: Analyzing Each Compound
We will analyze each compound to see if they contain acidic protons that can react with the Grignard reagent.

#### (a) `CH₃–CH₂–CH₂OH` (Propan-1-ol)
- This is an alcohol. The hydroxyl (OH) group has an acidic hydrogen (H⁺).
- Reaction:
- CH₃MgI + CH₃–CH₂–CH₂OH → CH₄ + CH₃–CH₂–CH₂O⁻MgI⁺
- Methane is liberated.

#### (b) `H₃C–CH₂–C≡CH` (1-Butyne)
- This is an alkyne. The terminal hydrogen (H) is acidic.
- Reaction:
- CH₃MgI + H₃C–CH₂–C≡CH → CH₄ + H₃C–CH₂–C≡C⁻MgI⁺
- Methane is liberated.

#### (c) `H₃C–CH₂–CO₂H` (Acetic Acid)
- This is a carboxylic acid. The acidic hydrogen (H) on the carboxyl group (COOH) can react.
- Reaction:
- CH₃MgI + H₃C–CH₂–CO₂H → CH₄ + H₃C–CH₂–COO⁻MgI⁺
- Methane is liberated.

#### (d) `H₃C–CH₂–CHO` (Acetaldehyde)
- This is an aldehyde. The hydrogen on the carbonyl (CHO) is not acidic enough to react with the Grignard reagent.
- Reaction:
- CH₃MgI + H₃C–CH₂–CHO does not liberate methane.
- No methane is liberated.

### Conclusion
From the analysis:
- Compounds (a), (b), and (c) liberate methane when treated with excess methyl magnesium iodide.
- Compound (d) does not liberate methane.

### Final Answer
The compounds that liberate methane are: **(a) `CH₃–CH₂–CH₂OH`, (b) `H₃C–CH₂–C≡CH`, and (c) `H₃C–CH₂–CO₂H`.**

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