Among (i) `C_(6)H_(5) NH_(2)` (ii) `CH_3NHCH_(3)` (iii) `(CH_3)_2NCH_(3) ` and (iv) `NH_3` , the correct order of basic strength follows the order

Options

A. `(ii) gt (iii) gt (iv) gt (i)`
B. `(ii) gt (iii) gt (i) gt (iv)`
C. `(iii) gt (ii) gt (iv) gt (i)`
D. `(iii) gt (ii) gt (i) gt (iv)`

Answer

To determine the correct order of basic strength among the given compounds:

1. **Identify the compounds**:
- (i) Aniline, C₆H₅NH₂
- (ii) N,N-Dimethylamine, CH₃NHCH₃
- (iii) N,N,N-Trimethylamine, (CH₃)₃N
- (iv) Ammonia, NH₃

2. **Understand basic strength**:
Basic strength is determined by the availability of the lone pair of electrons on the nitrogen atom in these compounds. The more available the lone pair, the stronger the base.

3. **Analyze each compound**:
- **Aniline (C₆H₅NH₂)**: The lone pair on nitrogen is involved in resonance with the benzene ring, reducing its availability for protonation. Thus, it is the least basic.
- **N,N-Dimethylamine (CH₃NHCH₃)**: The lone pair on nitrogen is not involved in resonance and is influenced by two methyl groups, which have a +I (inductive) effect, increasing the electron density on nitrogen. This makes it a stronger base than aniline.
- **N,N,N-Trimethylamine ((CH₃)₃N)**: Similar to dimethylamine, but with three methyl groups. While it has a higher electron density due to the +I effect, steric hindrance from the three bulky groups makes it slightly less basic than dimethylamine.
- **Ammonia (NH₃)**: It has a lone pair that is fully available for protonation, but it does not have any alkyl groups to enhance its basicity. It is more basic than aniline but less than the dimethylamine.

4. **Rank the basicity**:
Based on the analysis:
- N,N-Dimethylamine (CH₃NHCH₃) > N,N,N-Trimethylamine ((CH₃)₃N) > Ammonia (NH₃) > Aniline (C₆H₅NH₂)

5. **Final order**:
The correct order of basic strength is:
- CH₃NHCH₃ > (CH₃)₃N > NH₃ > C₆H₅NH₂

Thus, the final answer is:
**Order of basic strength: CH₃NHCH₃ > (CH₃)₃N > NH₃ > C₆H₅NH₂**