Chemistry (Year 12) - Organic Chemistry
Esters are effectively a hybrid between carboxylic acids and alcohols. A fruit odour characterises these compounds.
The ester functional group is created from the O atom of an alcohol functional group, bonded to the C atom of a carboxylic acid functional group. Esters hence have the general formula of R' - COO - R''.
Since esters result from two functional groups, they are named by first naming the alcohol group with the suffix 'yl' and then the carboxylic acid group with the suffix 'oate'.
Boiling Point of Esters
Esters only exhibit dispersion forces and dipole-dipole forces between their molecules.
The presence of dispersion forces and dipole-dipole forces make the attraction between ester molecules moderately strong, giving them a similar boiling point to aldehydes and ketones. When compared to alcohols and carboxylic acids, esters have a lower boiling point as they cannot form hydrogen bonds between their molecules.
Solubility of Esters
For solubility, esters can form hydrogen bonds between the lone pair electrons on their O atom and the H atoms of water. This gives them a similar solubility to aldehydes and ketones.
As esters do not have an H atom to form hydrogen bonds to the O atom in water, they form fewer hydrogen bonds per molecule and are therefore less soluble than alcohols and carboxylic acids.