9-Crown-3
9-Crown-3, also called 1,4,7-trioxonane or 1,4,7-trioxacyclononane, is a crown ether with the formula 3. A colorless liquid, it is obtained in low yield by the acid-catalyzed oligomerization of ethylene oxide.
In contrast to larger crown ethers, 9-crown-3 has elicited very little interest, except from theorists.