Correct sequence for reactivity of acid derivative is
(1) `(RCO)_2O`
(2) RCOCl
(3) RCOOR
(4) RCON`H_2`

Options

A. `2gt1gt3gt4`
B. `1gt2gt3gt4`
C. `2gt1gt4gt3`
D. `1gt3gt2gt4`

Answer

To determine the correct sequence for the reactivity of acid derivatives, we need to analyze the given compounds based on their structures and the basicity of their leaving groups.

### Step-by-Step Solution:

1. **Identify the Acid Derivatives**:
- (1) \( (RCO)_2O \) - Acid Anhydride
- (2) \( RCOCl \) - Acid Chloride
- (3) \( RCOOR \) - Ester
- (4) \( RCONH_2 \) - Amide

2. **Draw the Structures**:
- Acid Anhydride: \( R-C(=O)-O-C(=O)-R \)
- Acid Chloride: \( R-C(=O)-Cl \)
- Ester: \( R-C(=O)-O-R \)
- Amide: \( R-C(=O)-NH_2 \)

3. **Understand the Basicity of Leaving Groups**:
- The reactivity of these acid derivatives is influenced by the basicity of their leaving groups. The weaker the base, the better it is as a leaving group.
- Basicity order of leaving groups (from strongest to weakest):
- \( Cl^- \) (from Acid Chloride)
- \( RCOO^- \) (from Acid Anhydride)
- \( RO^- \) (from Ester)
- \( NH_2^- \) (from Amide)

4. **Reactivity Order Based on Leaving Group Basicity**:
- Since strong bases are poor leaving groups, we can arrange the reactivity of the acid derivatives as follows:
- **Most Reactive**: Acid Chloride \( (RCOCl) \) - because it has \( Cl^- \) as a leaving group.
- **Next**: Acid Anhydride \( ((RCO)_2O) \) - \( RCOO^- \) is a weaker base than \( RO^- \).
- **Then**: Ester \( (RCOOR) \) - \( RO^- \) is a stronger base than \( RCOO^- \).
- **Least Reactive**: Amide \( (RCONH_2) \) - \( NH_2^- \) is the strongest base and thus the least reactive.

5. **Final Order of Reactivity**:
- Based on the analysis, the correct sequence for reactivity of acid derivatives is:
- (2) \( RCOCl \) > (1) \( (RCO)_2O \) > (3) \( RCOOR \) > (4) \( RCONH_2 \)

### Conclusion:
The correct sequence for the reactivity of acid derivatives is **2, 1, 3, 4**.