Which of the following is a Lewis base

Options

A. `CH_(4)`
B. `C_(2)H_(5)OH`
C. Acetone
D. Secondary amine

Explanation

To determine which of the given options is a Lewis base, we need to understand that a Lewis base is defined as a species that can donate a pair of electrons. Let's analyze each option step by step:

### Step 1: Analyze CH₄ (Methane)
- **Structure**: CH₄ has no lone pairs of electrons.
- **Conclusion**: Since it cannot donate a pair of electrons, CH₄ is **not a Lewis base**.

### Step 2: Analyze C₂H₅OH (Ethanol)
- **Structure**: Ethanol has the formula C₂H₅OH. The oxygen atom in the hydroxyl group (-OH) has two lone pairs of electrons.
- **Conclusion**: The presence of lone pairs on oxygen means ethanol can donate a pair of electrons, making it a **Lewis base** (though a weak one).

### Step 3: Analyze (CH₃)₂CO (Acetone)
- **Structure**: Acetone has the formula (CH₃)₂CO. The oxygen atom in the carbonyl group (C=O) has a lone pair of electrons.
- **Conclusion**: The lone pair on oxygen allows acetone to act as a **Lewis base** (also a weak one).

### Step 4: Analyze Secondary Amine
- **Structure**: A secondary amine has the general formula R₂NH, where R represents alkyl groups. The nitrogen atom has a lone pair of electrons.
- **Conclusion**: The lone pair on nitrogen allows secondary amines to donate electrons, making them a **Lewis base** (though they can also act as weak acids).

### Final Conclusion
From the analysis:
- **Lewis Bases**: Ethanol (C₂H₅OH), Acetone ((CH₃)₂CO), and Secondary Amine.
- **Not a Lewis Base**: CH₄ (Methane).

### Answer
The options that are Lewis bases are **Ethanol (C₂H₅OH)**, **Acetone ((CH₃)₂CO)**, and **Secondary Amine**.