Esters are a group of organic compounds that contain the functional group —COO—.
☝️ The structure of esters looks like this ☝️
- R and R' are usually carbon chains.
- R and R' can be the same carbon chain, or they can also be different.
- R' cannot be H, since the compound would then become a carboxylic acid instead of an ester.
Formation of Esters
Esters are formed by the reaction between carboxylic acids and alcohols in the presence of an acid catalyst.
carboxylic acid + alcohol → ester + water
For example, the formation of ethyl propanoate from propanoic acid and ethanol looks like:
Naming of Esters
The names of esters consist of two parts:
— the first part indicates the length of the carbon chain in the alcohol, and the name ends in —yl
— the second part indicates the length of the carbon chain in the carboxylic acid, and the name ends in —oate
- Ethyl methanoate is formed from ethanol and methanoic acid.
- Propyl ethanoate is formed from propanol and ethanoic acid.
Properties of Esters
- Since esters have very weak attractive forces, they are very volatile.
- Esters have a very distinctive smell.