Which of the following alkenes will give anti-markownikoff's product as major product.

Options

A. `Cl-CH=CH_(2)`
B. `CH_(3)-O-CH=CH_(2)`
C. `NH_(2)-CH=CH_(2)`
D. `CF_(3)-CH=CH_(2)`

Answer

To determine which of the given alkenes will yield an anti-Markovnikov product as the major product, we need to analyze the substituents attached to each alkene and their effects on the reaction mechanism.

### Step-by-Step Solution:

1. **Understanding Anti-Markovnikov's Rule**:
- Anti-Markovnikov's rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom will add to the carbon with the greater number of hydrogen atoms, while the halogen will add to the carbon with fewer hydrogen atoms. This typically occurs in the presence of certain substituents that can stabilize the carbocation formed during the reaction.

2. **Identifying the Substituents**:
- We have four alkenes with different substituents:
- Option 1: Chlorine (Cl)
- Option 2: Methoxy group (OCH3)
- Option 3: Amino group (NH2)
- Option 4: Trifluoromethyl group (CF3)

3. **Evaluating the Minus I Effect**:
- The key to determining which alkene will favor the anti-Markovnikov product lies in the -I (inductive) effect of the substituents:
- **CF3**: Strong -I effect (electron-withdrawing)
- **Cl**: Moderate -I effect
- **OCH3**: Weak -I effect (electron-donating through resonance, but has a -I effect)
- **NH2**: Weak -I effect (electron-donating through resonance)

4. **Determining the Major Product**:
- The substituent with the strongest -I effect will stabilize the carbocation formed during the reaction. In this case, the CF3 group has the strongest -I effect, which will lead to the formation of the anti-Markovnikov product as the major product.
- The reaction can be represented as follows:
- For the alkene with CF3:
\[ \text{CF}_3\text{CH}=\text{CH}_2 + HX \rightarrow \text{CF}_3\text{CH}_2\text{CH}_2X \]
- Here, the positive charge will preferentially form on the carbon with more hydrogen atoms (the CH2 group).

5. **Conclusion**:
- Based on the analysis, the alkene with the CF3 substituent will yield the anti-Markovnikov product as the major product.

### Final Answer:
- **Option 4 (CF3)** is the correct answer.