Assertion (A) Among isomeric pentanes, 2, 2-dimethylpentane has highest boiling point.
Reason (R ) Branching does not affect the boiling point.

Options

A. Both A and B are correct and R is the correct explanation of A
B. Both A and R are not correct
C. Both A and R are not correct
D. A is not correct but R is correct

Explanation

To solve the assertion and reason question regarding the boiling points of isomeric pentanes, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Understand the Assertion
The assertion states that among isomeric pentanes, 2,2-dimethylpentane has the highest boiling point.

### Step 2: Analyze the Isomers of Pentane
Pentane (C5H12) has several structural isomers:
1. **n-Pentane**: CH3-CH2-CH2-CH2-CH3
2. **Isopentane (Methylbutane)**: CH3-CH(CH3)-CH2-CH3
3. **Neopentane (Dimethylpropane)**: (CH3)4C
4. **2,2-Dimethylpentane**: CH3-C(CH3)2-CH2-CH3

Among these, 2,2-dimethylpentane is the most branched isomer.

### Step 3: Understand the Effect of Branching on Boiling Point
Branching in hydrocarbons generally leads to a decrease in boiling point. This is because:
- More branching reduces the surface area available for intermolecular interactions (such as van der Waals forces).
- Lower surface area means that less energy (heat) is required to overcome these interactions, leading to a lower boiling point.

### Step 4: Compare Boiling Points
Since 2,2-dimethylpentane is the most branched isomer, it will have the lowest boiling point among the pentane isomers, contrary to the assertion that it has the highest boiling point.

### Step 5: Analyze the Reason
The reason states that branching does not affect the boiling point. This statement is incorrect because, as established, branching does affect the boiling point by decreasing it.

### Conclusion
Both the assertion (A) and the reason (R) are incorrect:
- Assertion (A) is incorrect because 2,2-dimethylpentane does not have the highest boiling point; it has the lowest.
- Reason (R) is incorrect because branching does affect the boiling point, and it generally decreases it.

### Final Answer
Both assertion and reason are incorrect. Therefore, the correct option is that both A and R are false.

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