Amongst the following, the amongst base in aquesous medium is….

Options

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

Explanation

To determine the strongest base in aqueous medium among the given options, we need to analyze the basicity of each amine based on the groups attached to the nitrogen atom. The basicity of amines is influenced by the electron-donating or electron-withdrawing effects of these groups.

### Step-by-Step Solution:

1. **Understanding Basicity**:
Basicity in amines is defined by the ability of the nitrogen atom to donate its lone pair of electrons. The more electron density on the nitrogen, the stronger the base.

2. **Identifying the Effects**:
- **+I Effect (Electron-donating)**: Groups that donate electron density to the nitrogen increase its basicity.
- **-I Effect (Electron-withdrawing)**: Groups that withdraw electron density from the nitrogen decrease its basicity.

3. **Analyzing Each Option**:
- **Option 1: CH3NH2 (Methylamine)**: The methyl group (CH3) exhibits a +I effect, which increases the basicity of the amine.
- **Option 2: CH2(CN)NH2 (Aminoacetonitrile)**: The cyanide group (CN) exhibits a -I effect, which decreases the basicity of the amine.
- **Option 3: (CH3)2NH (Dimethylamine)**: This amine has two methyl groups, both of which exhibit a +I effect. This significantly increases the electron density on the nitrogen, enhancing its basicity.
- **Option 4: C6H5NHCH3 (Aniline derivative)**: The phenyl group (C6H5) exhibits a -I effect due to resonance, which decreases the basicity, even though the methyl group has a +I effect.

4. **Comparing Basicity**:
- **CH3NH2** has a moderate basicity due to one +I effect.
- **CH2(CN)NH2** has low basicity due to the -I effect.
- **(CH3)2NH** has the highest basicity due to two +I effects.
- **C6H5NHCH3** has reduced basicity due to the -I effect from the phenyl group.

5. **Conclusion**:
Based on the analysis, **(CH3)2NH (Dimethylamine)** is the strongest base in aqueous medium among the given options due to the presence of two +I effect groups.

### Final Answer:
The strongest base in aqueous medium is **(CH3)2NH (Dimethylamine)**.