Arrange reactivity of given compounds in decreasing order for electrophilic addition reaction
`{:(1.C_(6)H_(5)-CH=CH_(2)" "2.C_(6)H_(5)-underset(CH_(3))underset("| ")"C "=CH-CH_(3)),(3.C_(6)H_(5)-underset(C_(6)H_(5))underset("| ")"C "=CH-CH_(3)" "4.CH_(2)=CH-NO_(2)):}`
Select the correct answer from codes given below

Options

A. 4, 1, 2, 3
B. 3, 2, 1, 4
C. 2, 3, 1, 4
D. 2, 3, 4, 1

Answer

To determine the reactivity of the given compounds in decreasing order for electrophilic addition reactions, we need to analyze the stability of the carbocations formed during the reaction. The more stable the carbocation, the more reactive the compound will be.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- 1: \( C_6H_5-CH=CH_2 \)
- 2: \( C_6H_5-CH(CH_3)-CH=CH-CH_3 \)
- 3: \( C_6H_5-C_6H_5-CH=CH-CH_3 \)
- 4: \( CH_2=CH-NO_2 \)

2. **Analyze Each Compound for Carbocation Stability**:
- **Compound 1**: \( C_6H_5-CH=CH_2 \)
- When the electrophile attacks, a carbocation is formed at the \( CH \) position. The benzene ring can stabilize this carbocation through resonance.
- **Compound 2**: \( C_6H_5-CH(CH_3)-CH=CH-CH_3 \)
- The carbocation formed here can be stabilized by both the benzene ring and the adjacent \( CH_3 \) group through hyperconjugation and resonance, making it more stable than compound 1.
- **Compound 3**: \( C_6H_5-C_6H_5-CH=CH-CH_3 \)
- This compound has two benzene rings, which can provide significant resonance stabilization to the carbocation formed. Thus, it is expected to be the most stable and reactive.
- **Compound 4**: \( CH_2=CH-NO_2 \)
- The nitro group (\( NO_2 \)) is a strong electron-withdrawing group, which destabilizes the carbocation formed during the electrophilic addition. Therefore, this compound is expected to be the least reactive.

3. **Order of Reactivity**:
- Based on the stability of the carbocations formed:
- **Most Stable**: Compound 3 (due to resonance stabilization from two benzene rings)
- **Next Stable**: Compound 2 (due to resonance and hyperconjugation)
- **Next Stable**: Compound 1 (due to resonance stabilization from one benzene ring)
- **Least Stable**: Compound 4 (due to destabilization from the nitro group)

4. **Final Arrangement**:
- The decreasing order of reactivity for electrophilic addition reactions is:
- \( C_6H_5-C_6H_5-CH=CH-CH_3 > C_6H_5-CH(CH_3)-CH=CH-CH_3 > C_6H_5-CH=CH_2 > CH_2=CH-NO_2 \)

### Answer:
The correct order of reactivity in decreasing order is:
**3 > 2 > 1 > 4**