Which of the following reacts with metal by displacing the hydrogen atom?

Options

A. `CH_4`
B. `C_2H_6`
C. `C_2H_4`
D. `C_2H_2`

Answer

To determine which of the given hydrocarbons reacts with metals by displacing hydrogen atoms, we need to analyze their hybridization and acidity. Let's go through the steps:

### Step 1: Identify the Compounds
The compounds given in the question are:
1. Methane (CH₄)
2. Ethane (C₂H₆)
3. Ethene (C₂H₄)
4. Ethyne (C₂H₂)

### Step 2: Determine the Hybridization
- **Methane (CH₄)**: The carbon is sp³ hybridized (25% s character).
- **Ethane (C₂H₆)**: Each carbon is also sp³ hybridized (25% s character).
- **Ethene (C₂H₄)**: Each carbon is sp² hybridized (33% s character).
- **Ethyne (C₂H₂)**: Each carbon is sp hybridized (50% s character).

### Step 3: Analyze the Acidity
The acidity of a compound is influenced by the s character of the hybridization. As the s character increases, the electronegativity of the carbon atom increases, which can lead to the hydrogen atom being more acidic (i.e., it can be displaced more easily).

- **Methane and Ethane**: With sp³ hybridization and low s character, these compounds do not exhibit acidic behavior.
- **Ethene**: With sp² hybridization, it has moderate acidity but is still not sufficiently acidic to displace hydrogen.
- **Ethyne**: With sp hybridization and high s character, ethyne has a significant acidic hydrogen. The electronegativity of carbon is high enough to pull the electron density towards itself, allowing the hydrogen to be released as H⁺ when reacting with metals.

### Step 4: Conclusion
Only **ethyne (C₂H₂)** can react with metals by displacing the hydrogen atom due to its acidic nature.

### Final Answer
**Ethyne (C₂H₂)** is the compound that reacts with metals by displacing the hydrogen atom.

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