15-Crown-5
15-Crown-5 is a crown ether: a ring-shaped molecule made from five units of ethylene oxide (chemical formula C10H20O5). It acts as a host that can grab certain metal ions inside its cavity, especially sodium (Na+). This binding often helps sodium salts dissolve in organic solvents when 15-crown-5 is present.
How it’s made: It can be prepared by a modified Williamson ether synthesis. It can also form by cyclic oligomerization of ethylene oxide in the presence of boron trifluoride gas.
What it binds: The crown ether fits Na+ well, but it can also accommodate first-row transition metal ions. When it binds metals, the resulting complexes often have the crown in the equatorial plane with additional ligands (often water) arranged around the metal, sometimes forming seven-coordinate structures and crystalline polymeric solids.
Examples and uses: Transition-metal perchlorate complexes with 15-crown-5 have been isolated, including cobalt, nickel, copper, and zinc systems. It can also isolate salts of oxonium ions; for example, one salt contains an oxonium water complex coordinated by two 15-crown-5 molecules.
Derivative: Benzo-15-crown-5 is a related compound used to form salts of carbido ligands, such as [K(benzo-15-crown-5)2]+.
This page was last edited on 3 February 2026, at 21:03 (CET).