Which of the following is most basic in nature ?

Options

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

Explanation

To determine which of the given compounds is the most basic in nature, we need to analyze the basicity of each compound based on the factors that influence basicity, particularly focusing on the availability of the lone pair of electrons on nitrogen and the presence of electron-donating or electron-withdrawing groups.

### Step-by-step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are:
- A) NH3 (Ammonia)
- B) CH3NH2 (Methylamine)
- C) (CH3)2NH (Dimethylamine)
- D) C6H5NH2 (Aniline)

2. **Determine the Structure and Electron Availability**:
- **NH3**: Has a lone pair of electrons on nitrogen. No electron-donating or withdrawing groups.
- **CH3NH2**: Has a lone pair of electrons on nitrogen and one methyl group which is an electron-donating group (via +I effect).
- **(CH3)2NH**: Has a lone pair of electrons on nitrogen and two methyl groups, which provide a stronger +I effect than one methyl group.
- **C6H5NH2**: Has a lone pair of electrons on nitrogen, but the lone pair can participate in resonance with the benzene ring, reducing its availability for protonation.

3. **Evaluate the Basicity**:
- Basicity increases with the availability of the lone pair of electrons on nitrogen.
- The presence of electron-donating groups (like methyl groups) increases basicity, while electron-withdrawing groups decrease it.
- In **C6H5NH2**, the lone pair is delocalized into the benzene ring, making it less available for bonding with protons, thus decreasing its basicity.

4. **Rank the Compounds**:
- **(CH3)2NH** (Dimethylamine) will be the most basic due to the presence of two electron-donating methyl groups, which enhance the availability of the lone pair.
- **CH3NH2** (Methylamine) is next, with one electron-donating methyl group.
- **NH3** (Ammonia) follows, as it has no substituents that enhance basicity.
- **C6H5NH2** (Aniline) is the least basic due to resonance stabilization of the lone pair.

5. **Conclusion**: The most basic compound among the options is **(CH3)2NH (Dimethylamine)**.