Sesquiterpenes

Part of speech: noun

Definitions

1. A class of organic compounds that consist of three isoprene units
2. Known for their role in the scent and flavor of various plants
3. Often found in essential oils and have potential medicinal properties

Etymology: "Sesquiterpenes" is the plural of "sesquiterpene," a chemical term built from "sesqui-," meaning "one and a half," and "terpene." The "one and a half" refers to molecular size: a terpene is built from isoprene units, each five carbons long, and a sesquiterpene contains three of them, fifteen carbons in all, which is one and a half times the twenty-carbon diterpenes built from four units. The naming follows the pattern of "monoterpene," which has two isoprene units, so the prefixes count the units rather than the carbons. The "sesqui-" prefix comes from Latin, where it meant "one and a half," and it is used in English in other words such as "sesquicentennial," a hundred-and-fiftieth anniversary. Chemists borrowed it because it neatly described the arithmetic of the molecule. Nothing about the word is a historical survival; it is a deliberate technical coinage that tells you how many units a molecule contains.

Synonyms: terpenes