Which of the following isomer has lowest boiling point ?

Options

A.
B.
C.
D.

Explanation

To determine which isomer has the lowest boiling point among the given isomers, we need to analyze the types of bonding present in each structure. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Isomers
We are given four isomers of the same compound. Let's denote them as A, B, C, and D. Each isomer has a different structure, which affects its physical properties, including boiling point.

### Step 2: Analyze Intermolecular and Intramolecular Hydrogen Bonding
- **Intermolecular Hydrogen Bonding**: This occurs between different molecules. It generally leads to higher boiling points because more energy is required to separate the molecules.
- **Intramolecular Hydrogen Bonding**: This occurs within a single molecule. It typically results in lower boiling points because the molecule is more stable and requires less energy to break apart.

### Step 3: Examine Each Isomer
- **Isomers A and B**: Both of these structures exhibit intermolecular hydrogen bonding. This means they will have relatively higher boiling points due to the strong attractions between the molecules.

- **Isomer C**: This isomer exhibits intramolecular hydrogen bonding. Since the hydrogen bonding occurs within the molecule itself, it is more stable and requires less energy to separate the molecules, leading to a lower boiling point.

- **Isomer D**: Similar to A and B, this isomer also shows intermolecular hydrogen bonding, contributing to a higher boiling point.

### Step 4: Conclusion
After analyzing the types of hydrogen bonding in each isomer:
- Isomers A, B, and D have higher boiling points due to intermolecular hydrogen bonding.
- Isomer C has the lowest boiling point because it has intramolecular hydrogen bonding, which requires less energy to break.

Thus, **the isomer with the lowest boiling point is C**.

### Final Answer
The isomer with the lowest boiling point is **C**.

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