The increasing basicity order of the following compounds is :
(A) `CH_(3)CH_(2)NH_(2)`
(B) `CH_(3)CH_(2)overset(underset(|)(CH_(2)CH_(3)))(NH)`
(C ) `H_(3)C-overset(underset(|)(CH_(3)))(N)-CH_(3)`
(D) `Ph-overset(underset(|)(CH_(3)))(N)-H`

Options

A. `D lt C lt A lt B`
B. `A lt B lt D lt C`
C. `A lt B lt C lt D`
D. `D lt C lt B lt A`

Answer

To determine the increasing basicity order of the given compounds, we will analyze each compound based on the general rules of basicity for amines.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- (A) `CH3CH2NH2` (Ethylamine - primary amine)
- (B) `CH3CH2N(CH2CH3)2` (Diethylamine - secondary amine)
- (C) `H3C-N(CH3)2` (Dimethylamine - tertiary amine)
- (D) `Ph-N(CH3)-H` (Anisidine - tertiary amine with resonance)

2. **Understanding Basicity in Amines**:
- Amines act as Lewis bases because they can donate a lone pair of electrons.
- Basicity is influenced by the presence of electron-donating groups (alkyl groups) and steric hindrance.
- Generally, the order of basicity for amines is:
- Secondary amines > Primary amines > Tertiary amines (due to steric hindrance).
- However, if the lone pair of electrons on nitrogen is involved in resonance (as in aromatic amines), the basicity decreases.

3. **Analyzing Each Compound**:
- **Compound A (Ethylamine)**: A primary amine with two alkyl groups. It is basic but less so than secondary amines.
- **Compound B (Diethylamine)**: A secondary amine with more electron-donating groups, making it more basic than primary amines.
- **Compound C (Dimethylamine)**: A tertiary amine. Although it has three alkyl groups, steric hindrance reduces its basicity compared to secondary amines.
- **Compound D (Anisidine)**: A tertiary amine where the lone pair on nitrogen is involved in resonance with the phenyl ring, making it the least basic.

4. **Ranking the Compounds**:
- Based on the analysis:
- **Least Basic**: D (due to resonance)
- **Next**: C (tertiary amine, steric hindrance)
- **Next**: A (primary amine)
- **Most Basic**: B (secondary amine)

5. **Final Order**:
- The increasing order of basicity is:
- D < C < A < B

### Conclusion:
The increasing basicity order of the compounds is:
**D < C < A < B**.