Which of the following is the strongest Bronsted base ?

Options

A.
B.
C.
D.

Explanation

To determine which of the following is the strongest Bronsted base, we will analyze the options based on the availability of lone pair electrons for donation. A Bronsted base is defined as a species that can accept protons (H⁺) and the strength of a Bronsted base is related to the availability of its electrons for donation.

### Step-by-Step Solution:

1. **Identify the Options**: Let's assume we have four options (A, B, C, D) containing nitrogen compounds with varying lone pair electron availability.

2. **Analyze Option A**:
- This nitrogen has a lone pair of electrons, but they are involved in resonance (delocalized).
- **Conclusion**: Since the lone pair is not available for donation, this option is not a strong base.

3. **Analyze Option B**:
- This nitrogen has a lone pair of electrons that are localized (not involved in resonance).
- **Conclusion**: This option can act as a good base due to the availability of the lone pair for donation.

4. **Analyze Option C**:
- Similar to Option A, this nitrogen's lone pair is delocalized due to resonance.
- **Conclusion**: This option is also not a strong base because the lone pair is not available for donation.

5. **Analyze Option D**:
- This nitrogen has a localized lone pair and is also attached to electron-donating groups (inductive effect).
- **Conclusion**: The presence of these +I groups increases the electron density and enhances the ability to donate electrons, making this option a strong base.

6. **Comparison**:
- Options B and D are both good bases, but Option D is stronger due to the +I groups that increase electron density and donation capability.

7. **Final Answer**:
- The strongest Bronsted base among the options is **Option D**.