Question

Which among the following has lowest boiling point?

• A. \(\text{CH}_3 - \text{O} - \text{CH}_2 - \text{CH}_3\)
• B. \(\text{CH}_3 - \text{COOH}\)
• C. \(\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{CH}_3\)
• D. \(\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{OH}\)

Hint:

For similar molecular masses: \[ \text{carboxylic acid} > \text{alcohol} > \text{ether} > \text{alkane} \] in boiling point.

Answer 1

The Correct Option is C

Concept:
Boiling point depends mainly on intermolecular forces.
• Carboxylic acids and alcohols show hydrogen bonding, so they have higher boiling points.
• Ethers are polar, so their boiling points are moderate.
• Alkanes are nonpolar and have only weak van der Waals forces, so they have lower boiling points.

Step 1: Check each compound.

• \(\text{CH}_3 - \text{O} - \text{CH}_2 - \text{CH}_3\) is an ether.
• \(\text{CH}_3 - \text{COOH}\) is a carboxylic acid.
• \(\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{CH}_3\) is an alkane.
• \(\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{OH}\) is an alcohol.

Step 2: Identify the compound with weakest intermolecular forces.
The alkane has only weak dispersion forces, so it has the lowest boiling point. Hence, the correct answer is:
\[ \boxed{(C)\ \text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{CH}_3} \]