Among the following amines, the strongest Bronsted base is….

Options

A.
B. `NH_(3)`
C.
D.

Explanation

To determine which among the given amines is the strongest Bronsted base, we will analyze each option based on their structure and the presence of electron-donating or electron-withdrawing effects.

### Step 1: Understand Bronsted Bases
A Bronsted base is defined as a substance that can accept protons (H⁺ ions). The strength of a Bronsted base is influenced by the availability of lone pairs of electrons on the nitrogen atom, as well as the presence of any electron-withdrawing or electron-donating groups that may stabilize or destabilize the lone pair.

### Step 2: Analyze Aniline
- **Structure**: Aniline (C₆H₅NH₂) has an amino group (-NH₂) attached to a benzene ring.
- **Effect of the Benzene Ring**: The lone pair of electrons on the nitrogen can be delocalized into the aromatic ring. This delocalization reduces the availability of the lone pair for protonation, making aniline less basic.
- **Conclusion**: Aniline is a weak base compared to ammonia.

### Step 3: Analyze Ammonia
- **Structure**: Ammonia (NH₃) has a lone pair of electrons on the nitrogen atom.
- **No Delocalization**: There are no aromatic rings or other groups that can delocalize the lone pair, making it readily available for protonation.
- **Conclusion**: Ammonia is a stronger base than aniline.

### Step 4: Analyze Pyrrole
- **Structure**: Pyrrole (C₄H₄NH) contains a nitrogen atom in a five-membered ring with two double bonds.
- **Effect of Conjugation**: The lone pair on nitrogen is involved in the aromaticity of the ring, which means it is less available for protonation.
- **Conclusion**: Pyrrole is a weak base due to the involvement of the lone pair in maintaining aromatic stability.

### Step 5: Analyze Pyrrolidine
- **Structure**: Pyrrolidine (C₄H₉N) is a saturated five-membered ring containing nitrogen.
- **No Delocalization**: The nitrogen's lone pair is not involved in any resonance or delocalization, making it highly available for protonation.
- **Conclusion**: Pyrrolidine is the strongest base among the options provided.

### Final Conclusion
Among the given amines, the strongest Bronsted base is **pyrrolidine**.