Markownikoff rule is best applicable to

Options

A. `C_(2)H_(4)+HCl`
B. `C_(3)H_(6)+Br_(2)`
C. `C_(3)H_(6)+HBr`
D. `C_(3)H_(6)+Cl_(2)`

Answer

To determine where Markovnikov's rule is best applicable, we need to analyze the given options and understand the rule itself. Markovnikov's rule states that when an unsymmetrical reagent adds to an unsymmetrical alkene, the electrophilic part of the reagent will attach to the carbon atom with the greater number of hydrogen atoms, while the nucleophilic part will attach to the carbon atom with fewer hydrogen atoms.

### Step-by-Step Solution:

1. **Identify the Reagents and Alkenes**:
- The first option is C2H4 (ethene) reacting with HCl.
- The second option is C3H6 reacting with Br2.
- The third option is C3H6 reacting with HBr.

2. **Analyze the First Option (C2H4 + HCl)**:
- Ethene (C2H4) has two carbon atoms, each bonded to two hydrogen atoms.
- When HCl reacts, the Cl- (nucleophilic part) would ideally go to the carbon with fewer hydrogens. However, both carbons have the same number of hydrogens (2 each).
- Therefore, Markovnikov's rule does not apply here because there is no preference for either carbon.

**Conclusion**: This option is not applicable.

3. **Analyze the Second Option (C3H6 + Br2)**:
- C3H6 (propene) is an alkene, but Br2 is a symmetrical reagent.
- In this case, there is no electrophilic addition mechanism that favors one carbon over another since both bromine atoms will add equally to the double bond.
- Thus, Markovnikov's rule does not apply here either.

**Conclusion**: This option is not applicable.

4. **Analyze the Third Option (C3H6 + HBr)**:
- Here, C3H6 is propene, which has a double bond between two carbon atoms.
- When HBr reacts, H+ (electrophilic part) will attach to the carbon with more hydrogen atoms, and Br- (nucleophilic part) will attach to the carbon with fewer hydrogen atoms.
- In propene, one carbon has 2 hydrogens and the other has 1 hydrogen. According to Markovnikov's rule, Br- will attach to the carbon with 1 hydrogen.

**Conclusion**: This option is applicable according to Markovnikov's rule.

5. **Final Answer**: The best application of Markovnikov's rule is in the reaction of C3H6 with HBr.