Conjugation of electron withdrawing groups, `e.e., -CHO, -overset(O)overset(||)C-R,-overset(O)overset(||)CRgt-overset(O)overset(||)C-OR,-C-=N,-NO_(2)` activates nudeophilic attack in halobenzene. The order of reactivity of these groups is :

Options

A. `-NO_(2)gt-C-=gt-overset(O)overset(||)C-Hgt-overset(O)overset(||)C-Rgt-overset(O)overset(||)C-OR`
B. `-overset(O)overset(||)C-Hgt-overset(O)overset(||)C-Rgt-overset(O)overset(||)C-ORgt-C-=Ngt-NO_(2)`
C. `-C-=Ngt-NO_(2)-overset(O)overset(||)C-Hgt-overset(O)overset(||)C-Rgt-overset(O)overset(||)C-OR`
D. `-overset(O)overset(||)-Hgt-NO_(2)gt-C-=Ngt-overset(O)overset(||)-ORgt-overset(O)overset(||)C-R`

Answer

To determine the order of reactivity of various electron-withdrawing groups (EWGs) in activating nucleophilic attack on halobenzenes, we need to consider the nature and strength of these groups. Here’s a step-by-step solution:

### Step 1: Identify the Electron-Withdrawing Groups
The groups mentioned in the question are:
- Aldehyde group (-CHO)
- Ketone group (-C(=O)R)
- Ester group (-C(=O)OR)
- Cyanide group (-C≡N)
- Nitro group (-NO₂)

### Step 2: Understand the Role of Electron-Withdrawing Groups
Electron-withdrawing groups decrease the electron density on the benzene ring. This makes the ring more susceptible to nucleophilic attack because it stabilizes the negative charge that forms during the reaction.

### Step 3: Rank the Electron-Withdrawing Groups by Strength
The strength of electron-withdrawing groups can be ranked based on their ability to stabilize the negative charge and their inductive or resonance effects. The general order from strongest to weakest is:
1. Nitro group (-NO₂) - Strongest due to resonance and inductive effects.
2. Cyanide group (-C≡N) - Strong electron-withdrawing due to the triple bond.
3. Aldehyde group (-CHO) - Moderate electron-withdrawing due to resonance.
4. Ketone group (-C(=O)R) - Similar to aldehyde but slightly weaker due to steric hindrance.
5. Ester group (-C(=O)OR) - Weakest among the listed groups due to resonance stabilization of the ring.

### Step 4: Write the Order of Reactivity
Based on the analysis above, the order of reactivity of the electron-withdrawing groups in activating nucleophilic attack in halobenzene is:
1. -NO₂ (Nitro group)
2. -C≡N (Cyanide group)
3. -CHO (Aldehyde group)
4. -C(=O)R (Ketone group)
5. -C(=O)OR (Ester group)

### Final Answer
The order of reactivity of the electron-withdrawing groups in activating nucleophilic attack in halobenzene is:
**-NO₂ > -C≡N > -CHO > -C(=O)R > -C(=O)OR**

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