Question

Which of the following compounds has the highest boiling point?

• A. n-Butane
• B. Propan-1-ol
• C. Methoxy methane
• D. Propanal
• E. Acetone

Hint:

The presence of hydrogen bonding generally results in higher boiling points. Alcohols usually have higher boiling points than aldehydes, ketones, and alkanes.

Answer 1

The Correct Option is B

Step 1: Understand the relationship between boiling points and intermolecular forces.
The boiling point of a compound is influenced by the strength of its intermolecular forces. Compounds with stronger intermolecular forces (such as hydrogen bonding) tend to have higher boiling points. The main types of intermolecular forces are:
- London dispersion forces (found in non-polar molecules),
- Dipole-dipole interactions,
- Hydrogen bonding (found in molecules with -OH or -NH groups).

Step 2: Examine the compounds.
- n-Butane: A simple alkane, it only experiences London dispersion forces. Alkanes generally have low boiling points.
- Propan-1-ol: An alcohol with a hydroxyl (-OH) group. The -OH group allows hydrogen bonding, which significantly increases its boiling point compared to non-polar molecules.
- Methoxy methane: An ether with no hydrogen bonding. It only experiences dipole-dipole interactions and London dispersion forces.
- Propanal: An aldehyde with a polar carbonyl group (C=O). It experiences dipole-dipole interactions but does not have hydrogen bonding.
- Acetone: A ketone, also with a polar carbonyl group (C=O). Like propanal, it has dipole-dipole interactions but lacks hydrogen bonding.

Step 3: Compare the boiling points.
Among the given compounds, propan-1-ol has the highest boiling point due to the presence of hydrogen bonding, which significantly increases the boiling point compared to other compounds that only have dipole-dipole interactions or dispersion forces.
Step 4: Final Answer.
Therefore, the compound with the highest boiling point is propan-1-ol.