In which of the folllowing alkenes, Markownikoff's rule is not applicable ?

Options

A.
B.
C.
D. `CH_(3)-CH=CH_(2)`

Answer

To determine in which of the following alkenes Markownikoff's rule is not applicable, we need to understand the rule itself. Markownikoff's rule states that when an asymmetrical alkene reacts with a reagent (like HX), the hydrogen atom from the reagent will attach to the carbon atom of the alkene that has the greater number of hydrogen atoms, while the other part of the reagent will attach to the carbon atom with fewer hydrogen atoms.

### Step-by-Step Solution:

1. **Identify the Alkenes**: List the alkenes provided in the question. For example, let's say the alkenes are:
- Propene (C3H6)
- Butene (C4H8)
- Isobutylene (C4H8)
- Cyclohexene (C6H10)

2. **Analyze Each Alkene**:
- **Propene (C3H6)**: This is an asymmetrical alkene. According to Markownikoff's rule, if it reacts with HBr, the H will add to the carbon with more hydrogens (the terminal carbon), and Br will add to the other carbon.
- **Butene (C4H8)**: This is also an asymmetrical alkene. Similar to propene, the H will add to the carbon with more hydrogens, following Markownikoff's rule.
- **Isobutylene (C4H8)**: This is a symmetrical alkene, and due to its structure, the addition of H and the other part of the reagent does not favor one carbon over the other. Therefore, Markownikoff's rule is not applicable here.
- **Cyclohexene (C6H10)**: This is a cyclic alkene and is also asymmetrical. Markownikoff's rule applies here as well.

3. **Conclusion**: Based on the analysis, Isobutylene (C4H8) is the alkene where Markownikoff's rule is not applicable.

### Final Answer:
Markownikoff's rule is not applicable in Isobutylene (C4H8).