Which of the following give Schiff base with aldehyde?

Options

A. `CH_3 CH_2 NH_2`
B. `C_6 H_5 - CH_2 - NH_2`
C. `C_6 H_5 - NH_2`
D. `C_6 H_5 - NO_2`

Explanation

To determine which of the given compounds can form a Schiff base with an aldehyde, we need to understand the general reaction involved in the formation of Schiff bases. Schiff bases are formed when a primary amine reacts with an aldehyde, resulting in the formation of an imine (C=N) and the release of water.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The general reaction for the formation of a Schiff base can be represented as:
\[ RNH_2 + R'CHO \xrightarrow{H^+} RNH=CHR' + H_2O \]
Here, \( RNH_2 \) is a primary amine and \( R'CHO \) is an aldehyde.

2. **Examine the Options**:
We need to check each option to see if they are primary amines. Primary amines can be either aliphatic or aromatic.

3. **Option 1: CH3CH2NH2 (Ethylamine)**:
- This is a primary amine (aliphatic).
- It can react with an aldehyde (e.g., acetaldehyde) to form a Schiff base.
- **Conclusion**: This option can form a Schiff base.

4. **Option 2: C6H5NH2 (Aniline)**:
- This is also a primary amine (aromatic).
- It can react with an aldehyde (e.g., benzaldehyde) to form a Schiff base.
- **Conclusion**: This option can form a Schiff base.

5. **Option 3: C6H5CH2NH2 (Benzylamine)**:
- This is a primary amine (aromatic).
- It can react with an aldehyde to form a Schiff base.
- **Conclusion**: This option can form a Schiff base.

6. **Option 4: NO2-Substituted Amine**:
- If this amine is a secondary or tertiary amine, it will not form a Schiff base.
- If it is a primary amine but has a strong electron-withdrawing group (like NO2), it may not react effectively with the aldehyde.
- **Conclusion**: This option does not form a Schiff base.

7. **Final Answer**:
The compounds that can form Schiff bases with aldehydes are:
- Option 1: CH3CH2NH2 (Ethylamine)
- Option 2: C6H5NH2 (Aniline)
- Option 3: C6H5CH2NH2 (Benzylamine)

Thus, the correct answer is **Options 1, 2, and 3**.