Mark the correct order of increasing reactivity.

Options

A. `CH_3 CONH_2 lt CH_2 COOC_2 H_5 lt CH_3 COCl`
B. `CH_3 COOC_2 H_5 lt CH_3 COCl lt CH_3 CONH_2`
C. `CH_3 COCl lt CH_3 CONH_2 lt CH_3 COOC_2 H_5`
D. `CH_3 COOC_2H_5 lt CH_3 CONH_2 lt CH_3 COCl`.

Explanation

To determine the correct order of increasing reactivity for the given acid derivatives (amide, ester, and acid chloride), we need to analyze the reactivity based on the stability of their leaving groups. Here’s the step-by-step solution:

### Step 1: Identify the Compounds
We have three acid derivatives:
1. Amide (RCONH2)
2. Ester (RCOOR')
3. Acid Chloride (RCOCl)

### Step 2: Understand the Leaving Groups
The reactivity of these compounds largely depends on the ability of their leaving groups to depart during a reaction. The more stable the leaving group, the more reactive the compound.

- **Amide**: The leaving group is NH2^− (amide ion), which is not very stable and does not leave easily.
- **Ester**: The leaving group is RO^− (alkoxide ion), which can leave but is more stable than NH2^−.
- **Acid Chloride**: The leaving group is Cl^− (chloride ion), which is very stable and can leave easily.

### Step 3: Rank the Leaving Groups
Based on the stability of the leaving groups, we can rank them:
1. Cl^− (from acid chloride) - most stable and leaves easily.
2. RO^− (from ester) - moderately stable and can leave.
3. NH2^− (from amide) - least stable and does not leave easily.

### Step 4: Determine Reactivity Order
Since the reactivity increases with the ease of leaving the group, we can conclude:
- Acid Chloride (most reactive)
- Ester (moderately reactive)
- Amide (least reactive)

### Step 5: Write the Increasing Order of Reactivity
Thus, the correct order of increasing reactivity is:
**Amide < Ester < Acid Chloride**

### Final Answer
The correct order of increasing reactivity is:
**Amide < Ester < Acid Chloride**