Which of the following has the lowest boiling points?

Options

A. 2-Methylbutane
B. 2-Methylpropane
C. 2,2-Dimethylpropane
D. n-Pentane

Explanation

To determine which of the given hydrocarbons has the lowest boiling point, we need to analyze the structure and molar mass of each compound. The compounds in question are:

1. 2-Methylbutane (C5H12)
2. 2-Methylpropane (C4H10)
3. 2,2-Dimethylpropane (C5H12)
4. n-Pentane (C5H12)

### Step 1: Identify the Molar Mass of Each Compound
- **2-Methylbutane (C5H12)**: Molar mass = 5(12) + 12(1) = 60 g/mol
- **2-Methylpropane (C4H10)**: Molar mass = 4(12) + 10(1) = 58 g/mol
- **2,2-Dimethylpropane (C5H12)**: Molar mass = 5(12) + 12(1) = 60 g/mol
- **n-Pentane (C5H12)**: Molar mass = 5(12) + 12(1) = 60 g/mol

### Step 2: Compare the Molar Masses
From the calculations, we find:
- 2-Methylbutane = 60 g/mol
- 2-Methylpropane = 58 g/mol
- 2,2-Dimethylpropane = 60 g/mol
- n-Pentane = 60 g/mol

### Step 3: Analyze the Structure and Branching
Boiling point is influenced by both molar mass and the degree of branching:
- **2-Methylbutane**: Has one branch.
- **2-Methylpropane**: Has a more branched structure compared to 2-Methylbutane.
- **2,2-Dimethylpropane**: Highly branched structure, which typically results in lower boiling points.
- **n-Pentane**: Straight-chain structure, which generally has a higher boiling point due to less branching.

### Step 4: Determine the Boiling Points
- Higher branching usually leads to lower boiling points.
- Since 2-Methylpropane is the most branched and has the lowest molar mass among the options with similar molar masses, it will have the lowest boiling point.

### Conclusion
Thus, the compound with the lowest boiling point among the given options is **2-Methylpropane (C4H10)**.

### Final Answer
**2-Methylpropane (C4H10) has the lowest boiling point.**

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