To determine the correct order of increasing boiling points for the isomeric compounds of \( C_5H_{12} \), we first need to identify the isomers of pentane and understand the factors that influence boiling points. ### Step 1: Identify the Isomers of \( C_5H_{12} \) The molecular formula \( C_5H_{12} \) corresponds to several structural isomers, which include: 1. **n-Pentane**: A straight-chain alkane. 2. **Isopentane (2-methylbutane)**: A branched isomer with a methyl group on the second carbon. 3. **Neopentane (2,2-dimethylpropane)**: A more branched isomer with two methyl groups on the second carbon. 4. **3-Methylbutane**: A branched isomer with a methyl group on the third carbon. ### Step 2: Understand Boiling Point Trends The boiling point of a compound is influenced by several factors, including: - **Molecular Weight**: Generally, as molecular weight increases, boiling points increase due to greater van der Waals forces. - **Branching**: More branched isomers tend to have lower boiling points than their straight-chain counterparts. This is because branching reduces the surface area available for intermolecular interactions, leading to weaker van der Waals forces. ### Step 3: Analyze Each Isomer 1. **n-Pentane**: This is the straight-chain isomer and has the highest boiling point among the isomers due to its larger surface area, which allows for stronger van der Waals interactions. 2. **Isopentane (2-methylbutane)**: This is a branched isomer and has a lower boiling point than n-pentane because the branching reduces the surface area for intermolecular interactions. 3. **3-Methylbutane**: Similar to isopentane, this is also a branched isomer and has a boiling point lower than n-pentane but slightly higher than neopentane due to its structure. 4. **Neopentane (2,2-dimethylpropane)**: This is the most branched isomer and has the lowest boiling point among the isomers due to its compact structure, which minimizes surface area and thus weakens van der Waals forces. ### Step 4: Order the Isomers by Boiling Point Based on the analysis above, we can order the isomers from lowest to highest boiling point: 1. **Neopentane (lowest boiling point)** 2. **Isopentane** 3. **3-Methylbutane** 4. **n-Pentane (highest boiling point)** ### Conclusion Thus, the correct order of increasing boiling point for the isomeric \( C_5H_{12} \) compounds is: **Neopentane < Isopentane < 3-Methylbutane < n-Pentane** ### Summary of Incorrect Options - **Option A (A)**: Likely refers to neopentane, which has the lowest boiling point. - **Option B (B)**: Could refer to isopentane, which has a higher boiling point than neopentane but lower than n-pentane. - **Option C (C)**: Could refer to 3-methylbutane, which has a boiling point higher than both neopentane and isopentane but lower than n-pentane. - **Option D (D)**: Refers to n-pentane, which has the highest boiling point among the isomers. ### Revision Summary - The boiling point of alkanes increases with molecular weight and decreases with increased branching. - n-Pentane has the highest boiling point due to its straight-chain structure. - Neopentane has the lowest boiling point due to its highly branched structure. - The order of boiling points for \( C_5H_{12} \) is: Neopentane < Isopentane < 3-Methylbutane < n-Pentane.