18-Crown-6 is an organic compound with the formula [CHO] and the IUPAC name of 1,4,7,10,13,16-hexaoxacyclooctadecane.  It is a white, hygroscopic crystalline solid with a low melting point. Like other crown ethers, 18-crown-6 functions as a ligand for some metal cations with a particular affinity for potassium cations (binding constant in methanol: 10 M).  The point group of 18-crown-6 is S. The dipole moment of 18-crown-6 varies in different solvent and under different temperature. Under 25 °C, the dipole moment of 18-crown-6 is  in cyclohexane and  in benzene. The synthesis of the crown ethers led to the awarding of the Nobel Prize in Chemistry to Charles J. Pedersen.