All of the following compounds have similar molar masses - HSC - SSCE Chemistry - Question 9 - 2019 - Paper 1

To determine which of the given compounds has the highest boiling point, we need to consider the types of intermolecular forces present in each compound.

1. Butane (C₄H₁₀): This molecule predominantly exhibits dispersion forces (London forces), which are relatively weak. Therefore, butane typically has a lower boiling point.

2. Ethanoic acid (C₂H₄O₂): Ethanoic acid can participate in hydrogen bonding due to the presence of the -OH (hydroxyl) group and the -COOH (carboxyl) group. Hydrogen bonds are significantly stronger than dispersion forces, resulting in a higher boiling point for ethanoic acid.

3. Propan-1-ol (C₃H₈O): Like ethanoic acid, propan-1-ol can also form hydrogen bonds due to the -OH group. However, its boiling point is lower than that of ethanoic acid due to having fewer intermolecular hydrogen bonds.

4. Propanone (C₃H₆O): Propanone (acetone) can polarize due to the carbonyl group (-C=O) resulting in dipole-dipole interactions, but lacks hydrogen bonding capability compared to the alcohols and acids.

Since ethanoic acid can form multiple hydrogen bonds, it exhibits the strongest intermolecular force out of all the options. Thus, ethanoic acid has the highest boiling point.