The boiling point of 2, 3-dimethylbutane is higher than that of 2,2-dimethylbutane.

Answer

To understand why the boiling point of 2,3-dimethylbutane is higher than that of 2,2-dimethylbutane, we need to analyze the structures of both compounds and the factors that affect boiling points.

### Step 1: Draw the Structures
1. **2,3-Dimethylbutane**:
- The main chain is butane (4 carbon atoms).
- The methyl groups (–CH₃) are attached to the 2nd and 3rd carbon atoms.
- Structure:
```
CH3
|
CH3-CH-CH-CH3
|
CH3
```

2. **2,2-Dimethylbutane**:
- The main chain is still butane.
- There are two methyl groups attached to the 2nd carbon atom.
- Structure:
```
CH3
|
CH3-C-CH2-CH3
|
CH3
```

### Step 2: Analyze Intermolecular Forces
- The boiling point of a substance is influenced by the strength of intermolecular forces.
- The primary intermolecular forces in hydrocarbons are Van der Waals (dispersion) forces.

### Step 3: Consider the Effect of Branching
- **2,3-Dimethylbutane** has less branching compared to **2,2-Dimethylbutane**.
- More branching leads to a smaller surface area, which reduces the strength of Van der Waals forces.
- In 2,2-dimethylbutane, the presence of two methyl groups on the same carbon creates a more compact structure, reducing the effective surface area for intermolecular interactions.

### Step 4: Compare Surface Areas
- **2,3-Dimethylbutane** has a larger surface area due to its less branched structure, allowing for stronger Van der Waals interactions.
- **2,2-Dimethylbutane** has a more branched structure, resulting in a smaller surface area and weaker interactions.

### Step 5: Conclusion
- Since 2,3-dimethylbutane has stronger intermolecular forces due to its larger surface area, it requires more energy to break these interactions, resulting in a higher boiling point compared to 2,2-dimethylbutane.

### Final Answer
The boiling point of 2,3-dimethylbutane is higher than that of 2,2-dimethylbutane because 2,3-dimethylbutane has a larger surface area leading to stronger Van der Waals forces, while 2,2-dimethylbutane has a more branched structure with a smaller surface area, resulting in weaker intermolecular interactions.

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