What are functional groups in organic chemistry?

Functional groups in organic chemistry are specific groups of atoms within molecules that determine their characteristics and chemical reactions.

In more detail, functional groups are the 'active parts' of organic molecules. They are specific clusters of atoms within a molecule that are responsible for the characteristic chemical reactions of that molecule. These groups of atoms are usually bonded together in a particular way, which gives the molecule its unique properties.

For instance, the hydroxyl (-OH) functional group makes a molecule an alcohol, and the carboxyl (-COOH) group makes it a carboxylic acid. These functional groups are the sites where chemical reactions occur, and they largely determine the molecule's physical and chemical properties, such as solubility, melting point, boiling point, density, and the types of chemical reactions it can undergo.

Functional groups are a critical concept in organic chemistry because they help us categorise and predict the behaviour of organic compounds. By identifying the functional groups in a molecule, we can predict how that molecule will react in different situations. This is because molecules with the same functional group will typically undergo similar types of reactions.

For example, all alcohols (molecules with a -OH functional group) can be oxidised to form aldehydes or carboxylic acids. Similarly, all carboxylic acids (molecules with a -COOH functional group) can react with alcohols to form esters.

In summary, functional groups are the key to understanding the behaviour of organic molecules. They are like the 'personality traits' of molecules, determining how they will interact with other molecules and the environment. By learning about different functional groups, you can start to predict and understand the vast world of organic chemistry.