What is cyclic compounds?

     A cyclic compound is a term for a compound in the field of chemistry in which one or more seires 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,(i.e., are carbocycles), none of the atoms are carbon  (inorganic cyclic compounds), or where both carbon and non-carbon atoms are present (heterocyclic compound).

     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 atom.  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 (e.g., <17 total atoms) number on the many billions.

     Adding to their complexity and number, closing of atoms into rings may lock particular atoms with distinct substitution (by functional groups) such that stereochemistry and chirality of the compound results, including some manifestations that are unique to rings (e.g., configurational isomers).  As well, depending on ring size, the three-dimensional shapes of particular cyclic structures-typically rings of 5-atoms and larger-can vary and interconvert such that conformational isomerism is displayed.  Indeed, the development of this important chemical concept arose, historically, in reference to cyclic compounds.  

Finally, cyclic compound, because of the unique shapes, reactivities, properties, and bioactibities that they engender, are the largest majority of all molecules involved in the biochemistry, structure, and function of living organisms, and in the man-made molecules (e.g., drugs, herbicides, etc.).