Question

Which of the following is the strongest Bronsted base?

• A.
• B.
• C.
• D.

Hint:

The strongest Bronsted base has a localized lone pair with minimal electron-withdrawing effects.

Answer 1

The Correct Option is D

Step 1: Understanding Bronsted Bases 
A Bronsted base is a substance that can accept protons. The strength of a Bronsted base depends on: 1. The availability of a lone pair for protonation. 2. The electron-donating or withdrawing effects of the surrounding groups. 
Step 2: Evaluating Each Structure 
Structure 1 has electron-withdrawing effects, reducing basicity. 
Structure 2 has delocalization of the lone pair, reducing its basicity.
Structure 3 is in a constrained ring, affecting electron availability. 
Structure 4 has a localized lone pair, making it the most basic. 
Thus, the correct answer is (D).