Rank the following compounds according to their boiling point.

propane

propanoic acid

propanal

1-propanol

Explanation:

Propane which is an alkane has the presence of van der waals or weak induced dipole - dipole interamolecular forces which are stronger as the carbon chain increases. This is due to the presence of more ions - electrons, protons etc.

Propanoic acid which is a member of the Carboxylic acids have much higher boiling points than all the others that is alkane, alcohols, aldehydes, or ketones of similar molecular weight. The difference is that the presence of two hydrogen bond, O-H as well as the C=O present in 1 molecule of carboxylic acid.

Propanol which is an Alcohol have higher boiling points than aldehydes and ketones of similar molecular weight. Thus, the dipole–dipole attractive forces of carbonyl compounds (H-C=O - aldehyde and C=O - ketone) are weaker than hydrogen-bonding interactions between alcohol molecule, O-H.

From the highest to the lowest,

Propanoic acid > 1-propanol > propanal > propane