Moiety (chemistry)


In organic chemistry, a moiety is a part of a molecule which is typically given a name as it can be found within other kinds of molecules as well.
The term moiety should be reserved to describe the larger characteristic parts of molecules and not used to describe smaller functional groups, which are made up of atoms that participate in similar chemical reactions in most molecules that contain them. In some instances moieties may be composed of yet smaller moieties and functional groups.
Moieties that constitute branches extending from the backbone of a hydrocarbon molecule, which can often be broken off and substituted with others, are called substituents or side chains.

Active moiety

In pharmacology, an active moiety is the part of a molecule or ion – excluding appended inactive portions – that is responsible for the physiological or pharmacological action of a drug substance. Inactive appended portions of the drug substance may include either the alcohol or acid moiety of an ester, a salt, or other noncovalent derivative. The parent drug may itself be an inactive prodrug and only after the active moiety is released from the parent in free form does it become active.