Which one of the following behaves as Lewis base as well as Bronsted-Lowry base ?

Options

A. Carbonium ion
B. Carbanion
C. Carbenium ion
D. All of these

Explanation

To determine which of the given options behaves as both a Lewis base and a Bronsted-Lowry base, we need to analyze each option based on their definitions.

### Step 1: Understand the Definitions
- **Lewis Base**: A Lewis base is defined as a species that is electron-rich and can donate a pair of electrons to another species.
- **Bronsted-Lowry Base**: A Bronsted-Lowry base is defined as a species that can accept a proton (H⁺).

### Step 2: Analyze Each Option
1. **Option A: Carbonium Ion (C⁺)**
- Structure: R₃C⁺ (where R represents alkyl groups)
- Analysis: Carbonium ions have a positive charge, indicating electron deficiency. They cannot donate electrons, so they do not qualify as Lewis bases. They can accept protons, so they can be Bronsted-Lowry bases, but they do not meet both criteria.

2. **Option B: Carbanion (C⁻)**
- Structure: R₃C⁻
- Analysis: Carbanions are negatively charged and have a lone pair of electrons, making them electron-rich. They can donate this lone pair, qualifying them as Lewis bases. Additionally, they can accept a proton to form a neutral molecule (e.g., CH₄), qualifying them as Bronsted-Lowry bases. Thus, carbanions behave as both.

3. **Option C: Carbenium Ion (C⁺)**
- Structure: R₃C⁺ (similar to carbonium ion)
- Analysis: Carbenium ions are also positively charged and thus electron-deficient. They cannot donate electrons, so they do not qualify as Lewis bases. They can accept protons, making them Bronsted-Lowry bases, but again, they do not meet both criteria.

4. **Option D: All of These**
- Analysis: Since only the carbanion qualifies as both a Lewis base and a Bronsted-Lowry base, this option is incorrect.

### Conclusion
Based on the analysis, the correct answer is **Option B: Carbanion (C⁻)**, as it behaves as both a Lewis base and a Bronsted-Lowry base.

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