Basicity of `CH_(3)CH_(2)NH_(2)(I),CH_(3)CONH_(2)(II)and C_(6)H_(5)CONH_(2)(III)` follows the order:

Options

A. `IgtIIgtIII`
B. `IgtIIIgtII`
C. `IIgtIIIgtI`
D. `IIIgtIIgtI`

Explanation

To determine the basicity of the compounds \( CH_3CH_2NH_2 \) (ethylamine), \( CH_3CONH_2 \) (acetamide), and \( C_6H_5CONH_2 \) (benzamide), we need to analyze the structure and electronic effects in each compound.

### Step 1: Identify the Compounds
- **Compound I**: Ethylamine \( (CH_3CH_2NH_2) \)
- **Compound II**: Acetamide \( (CH_3CONH_2) \)
- **Compound III**: Benzamide \( (C_6H_5CONH_2) \)

### Step 2: Analyze Basicity
Basicity in amines and amides is primarily determined by the availability of the lone pair of electrons on the nitrogen atom.

1. **Ethylamine \( (CH_3CH_2NH_2) \)**:
- The nitrogen atom has a lone pair that is localized and readily available for protonation.
- Alkyl groups are electron-donating, which increases the electron density on nitrogen, enhancing its basicity.

2. **Acetamide \( (CH_3CONH_2) \)**:
- The lone pair on nitrogen can participate in resonance with the carbonyl group \( (C=O) \).
- This resonance delocalizes the lone pair, making it less available for protonation compared to ethylamine. Thus, it is less basic than ethylamine.

3. **Benzamide \( (C_6H_5CONH_2) \)**:
- Similar to acetamide, the lone pair on nitrogen is also delocalized due to resonance with the carbonyl group.
- Additionally, the benzene ring can further delocalize the lone pair, reducing its availability even more than in acetamide. Therefore, benzamide is the least basic among the three.

### Step 3: Order of Basicity
Based on the analysis:
- **Most Basic**: Ethylamine \( (CH_3CH_2NH_2) \)
- **Moderately Basic**: Acetamide \( (CH_3CONH_2) \)
- **Least Basic**: Benzamide \( (C_6H_5CONH_2) \)

Thus, the order of basicity is:
\[ CH_3CH_2NH_2 > CH_3CONH_2 > C_6H_5CONH_2 \]

### Final Answer
The basicity follows the order:
\[ CH_3CH_2NH_2 > CH_3CONH_2 > C_6H_5CONH_2 \]

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