Among the amines (a) `C_(6)H_(5)NH_(2)` (b) `CH_(3)NH_(2)` (c) `(CH_(3))_(2)NH` (d) `(CH_(3))_(3)N` the order of basicity is

Options

A. `a lt b lt d lt c`
B. `d lt c lt b lt a`
C. `a gt b gt c gt d`
D. `b lt c lt d lt a`

Explanation

To determine the order of basicity among the given amines: (a) C₆H₅NH₂ (aniline), (b) CH₃NH₂ (methylamine), (c) (CH₃)₂NH (dimethylamine), and (d) (CH₃)₃N (trimethylamine), we can follow these steps:

### Step 1: Identify the Type of Amines
- **C₆H₅NH₂ (Aniline)**: This is a primary amine.
- **CH₃NH₂ (Methylamine)**: This is also a primary amine.
- **(CH₃)₂NH (Dimethylamine)**: This is a secondary amine.
- **(CH₃)₃N (Trimethylamine)**: This is a tertiary amine.

### Step 2: Consider the Availability of Lone Pair Electrons
The basicity of amines is largely influenced by the availability of the lone pair of electrons on the nitrogen atom:
- In **aniline (C₆H₅NH₂)**, the lone pair of electrons on nitrogen is delocalized into the benzene ring, which reduces its availability for protonation, making it less basic.
- In **methylamine (CH₃NH₂)**, the lone pair is fully available for bonding since there are no electron-withdrawing groups.
- In **dimethylamine ((CH₃)₂NH)**, the lone pair is also available, and the presence of two methyl groups provides some electron-donating effect, enhancing basicity.
- In **trimethylamine ((CH₃)₃N)**, the lone pair is still available, and the three methyl groups provide a strong electron-donating effect.

### Step 3: Compare the Basicities
- **Aniline (C₆H₅NH₂)** is the least basic due to the resonance stabilization of the lone pair.
- **Methylamine (CH₃NH₂)** is more basic than aniline because its lone pair is not involved in resonance.
- **Dimethylamine ((CH₃)₂NH)** is more basic than methylamine due to the electron-donating effect of two methyl groups.
- **Trimethylamine ((CH₃)₃N)** is the most basic because it has the highest number of electron-donating methyl groups, enhancing the availability of the lone pair.

### Final Order of Basicity
Based on the above analysis, the order of basicity is:
1. (CH₃)₃N (Trimethylamine) - Most basic
2. (CH₃)₂NH (Dimethylamine)
3. CH₃NH₂ (Methylamine)
4. C₆H₅NH₂ (Aniline) - Least basic

### Summary
The final order of basicity among the given amines is:
**(CH₃)₃N > (CH₃)₂NH > CH₃NH₂ > C₆H₅NH₂**