The exterior of these compounds is nonpolar, hydrophobic, and takes on a hydrocarbon character.
The so-called "linear" type of these compounds are known as glymes, which are super-effective at enhancing yields of processes like Ullmann couplings and Heck reactions. Reported in two landmark 1967 papers by Charles Pederson, their three-dimensional analogues are called cryptands, which also make use of nitrogen in complexing. The exterior of these compounds is nonpolar, hydrophobic, and takes on a hydrocarbon character. The notation system for them places their number of oxygen atoms last, and these oxygen atoms are crucial in coordinating with metal ions in their interior cavity. For ten points, name these heterocyclic compounds with repeating ethylene glycol units, a certain type of ethers named for their shape.
The so-called "linear" type of these compounds are known as glymes, which are super-effective at enhancing yields of processes like Ullmann couplings and Heck reactions.
{crown ethers} (or just crown at the end, prompt on ethers anytime)