The increasing basicity order of the following compounds is :
`(a) CH_3CH_2CH_2NH_2" "(b) CH_3CH_2overset(CH_2CH_3)overset(|)(NH)`
(c) `H_(3)C-overset(CH_3)overset(|)N-CH_3" (d) "Ph-overset(CH_3)overset(|)(N)-H`

Options

A. (a) (A) <(B) <(D) < (C )
B. (b) (A) < (B) < (C ) < (D)
C. (c) (D) < (C ) < (A) < (B)
D. (d) (D) < (C ) < (B) < (A)

Explanation

To determine the increasing basicity order of the given compounds, we need to analyze the structure of each amine and how their substituents affect their basicity. Basicity in amines is influenced by the ability of the nitrogen atom to donate its lone pair of electrons, which can be affected by steric hindrance and electron-donating or withdrawing effects.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- (a) CH₃CH₂CH₂NH₂ (Propylamine - Primary amine)
- (b) CH₃CH₂(N(CH₂CH₃)₂) (Diethylamine - Secondary amine)
- (c) H₃C(N(CH₃)₂) (Trimethylamine - Tertiary amine)
- (d) Ph(NHCH₃) (Aniline with a methyl group - Amine with electron-withdrawing resonance)

2. **Analyze Basicity Factors**:
- Basicity is influenced by the electron-donating ability of the groups attached to the nitrogen atom.
- Primary amines (like propylamine) have one alkyl group that donates electrons to the nitrogen, increasing its basicity.
- Secondary amines (like diethylamine) have two alkyl groups, which provide more electron donation than primary amines, thus increasing basicity further.
- Tertiary amines (like trimethylamine) have three alkyl groups, which would typically increase basicity, but the steric hindrance around the nitrogen atom can hinder the ability of the nitrogen to donate its lone pair effectively.
- Aniline (with a phenyl group) has resonance that delocalizes the lone pair of electrons on nitrogen, making it less available for donation, thus decreasing its basicity.

3. **Rank the Basicity**:
- **Aniline (d)**: Least basic due to resonance stabilization of the lone pair.
- **Trimethylamine (c)**: More basic than aniline but less than secondary amines due to steric hindrance.
- **Propylamine (a)**: More basic than trimethylamine due to less steric hindrance.
- **Diethylamine (b)**: Most basic due to the presence of two electron-donating groups and less steric hindrance compared to tertiary amines.

4. **Final Order of Basicity**:
- Increasing basicity order: **(d) < (c) < (a) < (b)**

### Conclusion:
The increasing basicity order of the compounds is: **(d) < (c) < (a) < (b)**.