Which of the following has a lower boiling point than ethanamine?

Propane

The correct answer is option 1. Propane.

To understand why propane has a lower boiling point than ethanamine, let’s consider the factors influencing boiling points, including intermolecular forces and molecular structure. The boiling point of a substance is influenced by the strength of the intermolecular forces holding its molecules together. Stronger intermolecular forces generally lead to higher boiling points.

Ethanamine (Ethylamine):

Boiling Point: Approximately 16.6°C (61.9°F).

Intermolecular Forces: Ethanamine has hydrogen bonding (due to the -NH2 group) and dipole-dipole interactions. Hydrogen bonding contributes to its relatively moderate boiling point.

Comparison of Boiling Points

1. Propane:

Boiling Point: Approximately -42°C (-43.6°F).

Intermolecular Forces: Propane is a nonpolar molecule with only London dispersion forces (van der Waals forces). These forces are weaker than hydrogen bonds, leading to a much lower boiling point.

2. Methanoic Acid (Formic Acid):

Boiling Point: Approximately 100.8°C (213.4°F).

Intermolecular Forces: Formic acid exhibits strong hydrogen bonding (due to both -OH and -COOH groups), which significantly raises its boiling point.

3. Ethanol:

Boiling Point: Approximately 78.4°C (173.1°F).

Intermolecular Forces: Ethanol also forms hydrogen bonds (due to the -OH group), leading to a higher boiling point compared to ethanamine.

4. Ethanal (Acetaldehyde):

Boiling Point: Approximately 20.2°C (68.4°F).

Intermolecular Forces: Ethanal has dipole-dipole interactions but no hydrogen bonding. Its boiling point is slightly higher than ethanamine due to these dipole interactions.

Summary of Why Propane Has a Lower Boiling Point

Intermolecular Forces: Propane has only weak London dispersion forces, whereas ethanamine has stronger hydrogen bonding.

Molecular Size: Propane is a smaller molecule compared to ethanamine and thus has less surface area for intermolecular interactions.

Since boiling points are influenced by intermolecular forces and propane has significantly weaker interactions compared to ethanamine, propane boils at a much lower temperature.

The correct compound with a lower boiling point than ethanamine is: Propane