Among the following compounds `C_(3)H_(7)NH_(2)NH_(3)CH_(3)NH_(2)C_(2)H_(5)NH_(2)` and `C_(6)H_(5)NH_(2)` the least basic compounds is .

Options

A. `C_(3)H_(7)NH_(2)`
B. `NH_(3)`
C. `CH_(3)NH_(2)`
D. `C_(6)H_(5)NH_(2)`

Answer

To determine which of the given compounds is the least basic, we need to analyze the basicity of each compound based on their structures and the influence of substituents on the nitrogen atom.

### Step 1: Identify the compounds
The compounds provided are:
1. C3H7NH2 (Propylamine)
2. NH3 (Ammonia)
3. CH3NH2 (Methylamine)
4. C2H5NH2 (Ethylamine)
5. C6H5NH2 (Aniline)

### Step 2: Understand basicity
Basicity in amines is influenced by the availability of the lone pair of electrons on the nitrogen atom. The more available the lone pair, the stronger the base. Factors that can affect this availability include:
- Inductive effects from alkyl groups (which can increase basicity).
- Resonance effects (which can decrease basicity).

### Step 3: Analyze each compound
1. **Propylamine (C3H7NH2)**: The alkyl group (propyl) is electron-donating, which increases the basicity.
2. **Ammonia (NH3)**: Ammonia has a lone pair available for donation, making it a weak base.
3. **Methylamine (CH3NH2)**: Similar to propylamine, the methyl group is also electron-donating, enhancing basicity.
4. **Ethylamine (C2H5NH2)**: The ethyl group is electron-donating, thus increasing basicity.
5. **Aniline (C6H5NH2)**: The phenyl group (C6H5) has resonance structures that delocalize the lone pair of electrons on nitrogen, making it less available for protonation. This significantly decreases its basicity.

### Step 4: Compare the basicity
- Propylamine, methylamine, and ethylamine are all stronger bases due to the electron-donating effect of their alkyl groups.
- Ammonia is a weak base but stronger than aniline.
- Aniline, due to resonance stabilization, has the least availability of the lone pair for protonation.

### Conclusion
Among the given compounds, **C6H5NH2 (Aniline)** is the least basic compound.

### Final Answer
The least basic compound among the given options is **C6H5NH2 (Aniline)**.

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