The correct order of increasing boiling point of the following compound is:

Pentan-1-ol, n-Butane, Pentanal, Ethoxyethane

n-Butane, Ethoxyethane, Pentanal, Pentan-1-ol

The correct answer is option 4. n-Butane, Ethoxyethane, Pentanal, Pentan-1-ol.

To determine the correct order of increasing boiling points of the compounds pentan-1-ol, n-butane, pentanal, and ethoxyethane, we need to consider the types of intermolecular forces each compound exhibits.

n-Butane \((C_4H_{10})\)

n-Butane is a non-polar alkane. Its intermolecular forces are limited to weak van der Waals (dispersion) forces. These weak forces result in a very low boiling point. It has the lowest boiling point among the given compounds.

Ethoxyethane (Diethyl ether, \(C_4H_{10}O\))

Ethoxyethane is an ether with an oxygen atom connecting two ethyl groups. The molecule is polar due to the C-O-C bond, leading to dipole-dipole interactions. While stronger than van der Waals forces, dipole-dipole interactions are not as strong as hydrogen bonding. It has a higher boiling point than n-butane but lower than those with hydrogen bonding.

Pentanal (\(C_5H_{10}O\))

Pentanal is an aldehyde with a polar carbonyl group (C=O). This group leads to dipole-dipole interactions. The carbonyl group creates a significant dipole, making these interactions stronger than those in ethers but still weaker than hydrogen bonding. Its boiling point is higher than that of ethoxyethane.

Pentan-1-ol (\(C_5H_{12}O\))

Pentan-1-ol is an alcohol with a hydroxyl group (-OH). This group enables the formation of hydrogen bonds. Hydrogen bonds are much stronger than both dipole-dipole interactions and van der Waals forces. It has the highest boiling point among the given compounds.

Putting it all together:

n-Butane: Lowest boiling point due to only weak van der Waals forces.

Ethoxyethane: Higher than n-butane due to dipole-dipole interactions.

Pentanal: Higher than ethoxyethane due to stronger dipole-dipole interactions from the carbonyl group.

Pentan-1-ol: Highest due to strong hydrogen bonding.

Therefore, the correct order of increasing boiling points is: n-Butane < Ethoxyethane < Pentanal < Pentan-1-ol

This corresponds to option: 4. n-Butane, Ethoxyethane, Pentanal, Pentan-1-ol