Functional Group
Definition and meaning of Functional Group in chemistry.
A functional group is a specific atom or group of atoms within a molecule that is responsible for the molecule's characteristic chemical reactions and properties, regardless of the size or structure of the rest of the molecule.
In more detail
Because a given functional group reacts in essentially the same way in any molecule that contains it, chemists use functional groups to classify organic compounds into families (alcohols, amines, ketones, carboxylic acids, and so on) and to predict how an unfamiliar molecule will behave. IUPAC nomenclature is organized around this idea: the highest-priority functional group present determines the compound's suffix (e.g., -ol, -al, -one, -oic acid). Many molecules, such as amino acids, are polyfunctional, containing more than one functional group, and each behaves largely independently of the others.
Key facts
| Field | Organic Chemistry |
|---|---|
| Common example | Hydroxyl group, -OH (alcohols) |
| Determines | Chemical reactivity and physical properties |
| Naming basis | Highest-priority group sets the IUPAC suffix (e.g., -oic acid > -al > -one > -ol) |
Ethanol, CH3CH2OH, contains a hydroxyl (-OH) functional group, which gives it the reactivity typical of alcohols, including oxidation to acetaldehyde and esterification with carboxylic acids to form esters.
Frequently asked questions
Can a molecule have more than one functional group?
Yes. Many organic molecules are polyfunctional; for example, amino acids contain both an amine (-NH2) and a carboxyl (-COOH) group, each reacting largely independently.
How is a functional group different from a substituent?
A functional group specifically confers characteristic chemical reactivity, while "substituent" is a broader term for any atom or group attached to a parent chain, including unreactive alkyl groups.