For ten points, name these compounds, named for their resemblance to royal headgear.
Charles Pedersen shared the 1987 Nobel Prize in Chemistry for their discovery, in which his strategy for their synthesis was to link catechols via hydroxyl groups. The 18-6 type is notably toxic to humans and exemplifies how these compounds are capable of coordinating with a wide variety of alkali metal cations. They are always composed of a number of ethyleneoxy units linked together in a ring, and rings featuring internal oxygens characterize them. For ten points, name these compounds, named for their resemblance to royal headgear.
Charles Pedersen shared the 1987 Nobel Prize in Chemistry for their discovery, in which his strategy for their synthesis was to link catechols via hydroxyl groups.
crown ethers [or crown compounds]