Closed chains are also called cyclic chains.
They present their atoms bonded together forming a geometric figure or ring cycle.
They can be classified according to the presence of an aromatic ring or not.
- alicyclic or non-aromatic - are closed chains that do not have the bezene ring.
- aromatic - are closed chains that have the aromatic ring or benzene ring. They have resonance between their electrons. These chains generally have six carbon atoms that alternate double bonds and single bonds.
Aromatic chains can be classified according to the number of aromatic rings:
- mononuclear: when it has only one core (aromatic ring)
- polynuclear: when you have several aromatic rings.
Polynuclear aromatics can be classified into:
- isolated polynuclear: when the rings have no carbon atom in common.
- condensed polynuclear: when the rings have carbon atoms in common.