9-Crown-3

9-Crown-3, also called 1,4,7-trioxonane or 1,4,7-trioxacyclononane is a crown ether with the formula (C2H4O)3. A colorless liquid, it is obtained in low yield by the acid-catalyzed oligomerization of ethylene oxide.

In contrast to larger crown ethers (12-crown-4, and 18-crown-6), 9-crown-3 has elicited very little interest, except from theorists.