The correct reactivity order for electrophilic addition reaction of following compound is:

Q: The correct reactivity order for electrophilic addition reaction of following compound is:

The correct reactivity order for electrophilic addition reaction of following compound is:

Question

Accepted Answer

To determine the correct reactivity order for the electrophilic addition reaction of the given compounds, we need to consider the stability of the carbocation intermediates formed during the reaction and the electron-donating or withdrawing effects of substituents.

1. **Compound (I): $PhCH=CH_{2}$**  
   - This compound is styrene, where the phenyl group ($Ph$) is attached to the vinyl group ($CH=CH_{2}$). The phenyl group can stabilize the carbocation formed during the reaction through resonance, but it is less effective compared to compounds with more substituted alkenes.

2. **Compound (II): $Ph-C(CH_3)=CH-CH_{3}$**  
   - This compound has a phenyl group and a methyl group attached to the double bond. The presence of the phenyl group provides resonance stabilization, and the additional methyl group offers hyperconjugation and inductive effects, making the carbocation more stable than in compound (I).

3. **Compound (III): $Ph_{2}C=CH-CH_{3}$**  
   - This compound has two phenyl groups attached to the carbon bearing the double bond. The presence of two phenyl groups provides significant resonance stabilization to the carbocation, making it highly stable and more reactive in electrophilic addition reactions compared to compounds (I) and (II).

4. **Compound (IV): $CH_{2}=CH-NO_{2}$**  
   - This compound has a nitro group ($NO_{2}$) attached to the vinyl group. The nitro group is a strong electron-withdrawing group, which destabilizes the carbocation formed during the reaction, making it the least reactive among the given compounds.

**Explanation for Option 2: $III>II>I>IV$**

- **Compound (III)** is the most reactive due to the presence of two phenyl groups, which provide excellent resonance stabilization to the carbocation, making it highly stable.
- **Compound (II)** is the next most reactive because it has both a phenyl group and a methyl group, offering a combination of resonance and hyperconjugation stabilization.
- **Compound (I)** follows, as it has only one phenyl group for resonance stabilization, making it less reactive than compounds (II) and (III).
- **Compound (IV)** is the least reactive due to the electron-withdrawing effect of the nitro group, which destabilizes the carbocation.

**Why Other Options Are Incorrect:**

- **Option 1 ($IV>I>II>III$):** This order incorrectly places compound (IV) as the most reactive, despite its destabilizing nitro group, and compound (III) as the least reactive, despite its high resonance stabilization.
- **Option 3 ($II>III>I>IV$):** This order incorrectly places compound (II) as more reactive than compound (III), despite compound (III) having greater resonance stabilization due to two phenyl groups.
- **Option 4 ($II>I>III>IV$):** This order incorrectly places compound (I) as more reactive than compound (III), despite compound (III) having superior resonance stabilization.

Thus, Option 2 ($III>II>I>IV$) is the correct reactivity order for the electrophilic addition reaction of the given compounds.