Which one of the following alkenes when treated with HCI yields majorly an anti-Markownikoff product:
1.CH_3O - CH = CH_2`
2.`H_2N - CH = CH_2`
3.`F_3C - CH =CH_2`
4.`Cl - CH = CH_2`

Options

A. `CH_3O - CH = CH_2`
B. `H_2N - CH = CH_2`
C. `F_3C - CH =CH_2`
D. `Cl - CH = CH_2`

Answer

To determine which alkene yields a major anti-Markovnikov product when treated with HCl, we need to analyze each option based on the stability of the carbocation formed and the nature of substituents attached to the double bond.

### Step-by-Step Solution:

1. **Understanding Anti-Markovnikov Addition**:
- Anti-Markovnikov addition refers to the addition of HCl to an alkene where the hydrogen (H) attaches to the carbon with more hydrogen atoms, and the chlorine (Cl) attaches to the carbon with fewer hydrogen atoms. This typically occurs in the presence of peroxides or with certain substituents that stabilize the carbocation.

2. **Analyzing Each Option**:
- **Option 1: CH₃O-CH=CH₂**
- The alkene part is CH=CH₂. The -OCH₃ group is an electron-donating group (due to +R effect).
- When HCl is added, the more stable carbocation formed will have the Cl attached to the carbon with fewer hydrogens, which does not follow the anti-Markovnikov rule. Thus, this option is incorrect.

- **Option 2: H₂N-CH=CH₂**
- The alkene part is CH=CH₂. The -NH₂ group is also an electron-donating group.
- Similar to the first option, the carbocation formed will have Cl attached to the carbon with fewer hydrogens, which again does not follow the anti-Markovnikov rule. Thus, this option is incorrect.

- **Option 3: F₃C-CH=CH₂**
- The alkene part is CH=CH₂. The -CF₃ group is a strong electron-withdrawing group.
- When HCl is added, the more stable carbocation will be formed by placing the CF₃ group away from the carbocation center, allowing Cl to attach to the carbon with more hydrogen atoms. This follows the anti-Markovnikov rule, making this option correct.

- **Option 4: Cl-CH=CH₂**
- The alkene part is CH=CH₂. The -Cl group has both -I (inductive) and +R (resonance) effects.
- The carbocation formed will also lead to Cl attaching to the carbon with fewer hydrogens, which does not follow the anti-Markovnikov rule. Thus, this option is incorrect.

3. **Conclusion**:
- The only alkene that yields a major anti-Markovnikov product when treated with HCl is **Option 3: F₃C-CH=CH₂**.

### Final Answer:
The correct option is **3. F₃C-CH=CH₂**.