Choose the strongest base among the following:

Options

A.
B.
C.
D.

Answer

To determine the strongest base among the given options, we need to analyze the structures and the availability of lone pairs of electrons for donation. Here’s a step-by-step solution:

### Step 1: Identify the Structures
We have four different structures (let's label them A, B, C, and D). Each structure contains a nitrogen atom with a lone pair of electrons.

### Step 2: Analyze the Lone Pairs
- **Structure A**: Contains a nitrogen atom with a lone pair that can easily donate to form a bond. This lone pair is not involved in resonance, making it a strong base.
- **Structure B**: Also has a nitrogen atom with a lone pair, but this lone pair can participate in resonance with the benzene ring, reducing its availability for donation.
- **Structure C**: Similar to structure B, the lone pair on nitrogen can participate in resonance with the aromatic system, making it less basic.
- **Structure D**: Contains a nitrogen atom with a lone pair that does not participate in resonance. This lone pair is fully available for donation, making it a strong base.

### Step 3: Compare the Basicity
- **Structure A**: Strong base due to the availability of the lone pair.
- **Structure B**: Weaker base due to resonance involvement.
- **Structure C**: Weaker base due to resonance involvement.
- **Structure D**: Strongest base as the lone pair is not involved in resonance and is fully available for donation.

### Step 4: Conclusion
After analyzing all four structures, we conclude that **Structure D** is the strongest base because its lone pair of electrons is readily available for donation without any resonance interference.

### Final Answer
**The strongest base among the given options is Structure D.**