The one which is the least basic

Options

A. `NH_(3)`
B. `C_(6)H_(5)NH_(2)`
C. `(C_(6)H_(5))_(3)N`
D. `(C_(6)H_(5))_(2)NH`

Answer

To determine which amine is the least basic among the given options, we need to analyze the basicity of each compound based on their structure and the presence of electron-withdrawing or electron-donating groups.

### Step-by-Step Solution:

1. **Understanding Basicity**:
Basicity in amines is primarily determined by the availability of the lone pair of electrons on the nitrogen atom to accept protons (H⁺). The more available the lone pair, the stronger the base.

2. **Analyzing Ammonia (NH₃)**:
- Ammonia has a lone pair of electrons on nitrogen that is readily available for donation.
- Therefore, ammonia is a strong base.

3. **Analyzing Aniline (C₆H₅NH₂)**:
- In aniline, one hydrogen atom of ammonia is replaced by a benzene ring.
- The lone pair of electrons on nitrogen can participate in resonance with the benzene ring, leading to delocalization of the electrons.
- This delocalization reduces the availability of the lone pair for protonation, making aniline less basic than ammonia.

4. **Analyzing Diphenylamine (C₆H₅NH(C₆H₅))**:
- In diphenylamine, two hydrogen atoms of ammonia are replaced by two benzene rings.
- The presence of two electron-withdrawing benzene rings further delocalizes the lone pair on nitrogen, making it even less available for donation than aniline.
- Thus, diphenylamine is less basic than aniline.

5. **Analyzing Triphenylamine (C₆H₅)₃N**:
- In triphenylamine, all three hydrogen atoms of ammonia are replaced by three benzene rings.
- The lone pair of nitrogen is highly delocalized due to resonance with all three benzene rings, making it the least available for donation.
- Therefore, triphenylamine is the least basic among all the options.

### Conclusion:
The compound that is the least basic is **Triphenylamine (C₆H₅)₃N**.

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