page_title: Cyclic compound
section_title: Macrocycles
hierarchical_section_title: Cyclic compound / Macrocycles
caption_attribution_description: English: Macrocyclic structures (in inorganic and supramolecular chemistry), an example array. These representations of macrocyclic compounds were revised from existing File:Macrocycles.svg, for use on English wikipedia. Changes: Danish legend was removed, with the following key/text allowing for use in en.wikipedia and other venues: A, the crown ether, 18-crown-6; B, the simple tetra-aza chelator, cyclam; C, an example porphyrin, the unsubstituted porphine; D, the mixed amine/imine,the Curtis macrocycle; E, the related enamine/imine Jäger macrocycle, and F, the tetracarboxylate-derivative DOTA macrocycle. [File created from available individual chemistry graphic file, by simple editing in GraphicConverter9.] Le Prof
context_page_description: A cyclic compound is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon, none of the atoms are carbon, or where both carbon and non-carbon atoms are present. Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic, in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size numbers in the many billions.
  Adding to their complexity and number, closing of atoms into rings may lock particular atoms with distinct substitution such that stereochemistry and chirality of the compound results, including some manifestations that are unique to rings.
context_section_description: The term macrocycle is used for compounds having a rings of 8 or more atoms. Macrocycles may be fully carbocyclic, heterocyclic but having limited heteroatoms (e.g., in lactones and lactams), or be rich in heteroatoms and displaying significant symmetry (e.g., in the case of chelating macrocycles). Macrocycles can access a number of stable conformations, with preference to reside in conformations that minimize transannular nonbonded interactions within the ring (e.g., with the chair and chair-boat being more stable than the boat-boat conformation for cyclooctane, because of the interactions depicted by the arcs shown). Medium rings (8-11 atoms) are the most strained, with between 9-13 (kcal/mol) strain energy, and analysis of factors important in the conformations of larger macrocycles can be modeled using medium ring conformations. Conformational analysis of odd-membered rings suggests they tend to reside in less symmetrical forms with smaller energy differences between stable conformations.
caption: Chelating macrocyclic structures of interest in inorganic and supramolecular chemistry, an example array. A, the crown ether, 18-crown-6;  B, the simple tetra-aza chelator, cyclam;  C, an example porphyrin, the unsubstituted porphine;  D, a mixed amine/imine, the Curtis macrocycle;  E, the related enamine/imine Jäger macrocycle, and  F, the tetracarboxylate-derivative DOTA macrocycle.
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