Which of the following is the correct increasing order of boiling point of following compounds ?
I `CH_(3) - CH_(2) -CH_(2)OH`, II `CH_(3)-underset(OH)underset(|)(CH)-CH_(3)` , III `CH_(3)-O-CH_(2)-CH_(3)`

Options

A. `II lt I lt III`
B. `III lt II lt I`
C. `I lt II lt III`
D. `II lt III lt I`

Answer

To determine the correct increasing order of boiling points for the given compounds, we need to analyze the structure and type of each compound:

1. **Identify the Compounds**:
- **Compound I**: `CH₃-CH₂-CH₂OH` (1-propanol) - This is a primary alcohol.
- **Compound II**: `CH₃-CH(OH)-CH₃` (2-propanol) - This is a secondary alcohol.
- **Compound III**: `CH₃-O-CH₂-CH₃` (ethyl methyl ether) - This is an ether.

2. **Understand the Properties**:
- Alcohols generally have higher boiling points than ethers due to the presence of intermolecular hydrogen bonding in alcohols. Ethers do not form hydrogen bonds as effectively.
- Among alcohols, primary alcohols typically have higher boiling points than secondary alcohols because primary alcohols can form more extensive hydrogen bonding networks.

3. **Comparing the Boiling Points**:
- **Compound III (Ether)**: Ethers have the lowest boiling points among the three compounds due to the absence of hydrogen bonding.
- **Compound II (2-Propanol, Secondary Alcohol)**: Secondary alcohols have higher boiling points than ethers but lower than primary alcohols.
- **Compound I (1-Propanol, Primary Alcohol)**: Primary alcohols have the highest boiling points due to their ability to form stronger hydrogen bonds.

4. **Conclusion**:
- Based on the analysis, the correct increasing order of boiling points is:
- **Compound III (Ether)** < **Compound II (2-Propanol)** < **Compound I (1-Propanol)**

Thus, the correct increasing order of boiling points is:
**III < II < I**