Anti-Markownikoff's addition of HBr is not observed in

Options

A. Pent-2-ene
B. Propane
C. But-2-ene
D. But-1-ene

Answer

To solve the question regarding the anti-Markovnikov addition of HBr, we need to analyze the conditions under which this type of addition occurs and identify which option does not fit these conditions.

### Step-by-Step Solution:

1. **Understand Anti-Markovnikov's Rule**:
- Anti-Markovnikov's addition refers to the addition of HBr to alkenes in such a way that the hydrogen atom adds to the carbon with fewer hydrogen atoms (the less substituted carbon), while the bromine adds to the more substituted carbon. This is typically observed in unsymmetrical alkenes in the presence of peroxides.

2. **Identify Symmetrical vs. Unsymmetrical Alkenes**:
- Symmetrical alkenes have identical groups on either side of the double bond, meaning that there is no preferential site for the addition of HBr. In contrast, unsymmetrical alkenes have different groups attached to the carbons involved in the double bond, allowing for the application of Markovnikov's or Anti-Markovnikov's rule.

3. **Analyze the Given Options**:
- We need to look at the options provided in the question (not listed here) and determine which one represents a symmetrical alkene.

4. **Conclusion**:
- The symmetrical alkene will not exhibit anti-Markovnikov addition of HBr because there is no difference in substitution at the two carbons of the double bond. Thus, the addition will not favor one carbon over the other.

5. **Final Answer**:
- Based on the analysis, the answer is option C, which represents a symmetrical alkene where anti-Markovnikov's addition does not occur.