Pyrylium

Part of speech: noun

Definitions

1. A positively charged six-membered oxygen-containing aromatic ring ion that forms the basis of certain dyes and salts used in chemistry
2. The cationic heterocyclic compound built from a pyran ring, known for its role in pigments and organic synthesis reagents
3. An aromatic oxonium ion with a single oxygen atom in its ring, employed in chemical research and in certain dye formulations

Etymology: Pyrylium is a chemist's coinage, not an ancient word, and its name points straight to its parent compound, pyrylium being built from "pyrylo-" and the suffix "-ium". The "pyryl-" part comes from "pyrone," a name chemists gave to a family of oxygen-containing six-membered rings, itself built from "pyro-" (from Greek "pyr," meaning fire) and the suffix for ketone-type compounds. The fire in the name is a little misleading: pyrones were named for their origin in the dry distillation of organic material, where heat is applied, not for any fiery character of the molecules. The "-ium" ending was chosen to mark the ring as a positively charged cation, following the convention used for ammonium, where the nitrogen atom carries a positive charge and the suffix signals it. Pyrylium salts were studied in the twentieth century, and the cation is an aromatic ring containing a positively charged oxygen atom, which is unusual because oxygen normally forms only two bonds. The name therefore carries a small piece of chemical bookkeeping: a ring related to pyrone, with an "-ium" ending for its positive charge.