Nomenclature of Cation-Binding Macrocycles

The naming of crown ethers is relatively simple, although for historical reasons it is only unambiguous if the exclusive use of ethylene glycol (—OCH2CH2O—) linkages is assumed in more complicated cases, the name is usually accompanied by a pictorial representation. 

The first number in the crown name designates the number of atoms in the ring (usually given in square brackets). 

The second number gives the number of oxygen (or other donor) atoms. 

Substituents are denoted with a prefix such as benzo-, dicyclohexano- etc. 

For example, dibenzo[18]crown-6 is a crown ether with an 18-membered macrocyclic ring containing six oxygen atoms with two benzo substituents. A more generalised system of nomenclature for such neutral organic ligands was developed by Vogtle and Weber, and later modified by in which 

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