Moiety (chemistry)

Typically, the term is used to describe the larger and characteristic parts of organic molecules, and it should not be used to describe or name smaller functional groups [1][2] of atoms that chemically react in similar ways in most molecules that contain them.

[citation needed] A moiety that acts as a branch extending from the backbone of a hydrocarbon molecule is called a substituent or side chain, which typically can be removed from the molecule and substituted with others.

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 (including a salt with hydrogen or coordination bonds), or other noncovalent derivative (such as a complex, chelate, or clathrate).

[4][5] 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.

Benzyl acetate contains a benzyloxy moiety (encircled with light orange). It also contains an ester functional group (in red), and an acetyl functional group (encircled with dark green). Other divisions can be made.