Heterocyclic compounds are substances which contain a ring structure as found in benzene and the aromatic compounds, or aromatic hydrocarbons, but in which other atoms than carbon, such as sulfur, oxygen or nitrogen are found as part of the ring. Some examples are pyridine (C5H5N) and pyrimidine (C4H4N2).
Note that compounds such as cyclopropane, an anaesthetic with explosive properties, and cyclohexane, a solvent, are not heterocyclic, they are merely cycloalkanes. The suffix '-cyclic' implies a ring structure, while 'hetero' refers to an atom other than carbon, as above.
In chemistry, a heterocyclic ring is a ring-like backbone whose atoms are not all of the same element.
Thus, the location of a fused ring may be indicated by a lowercase letter which designates the edge of the heterocyclic ring involved in the fusion, as shown by the pyridine ring in the green shaded box.
An important characteristic of aromaticity is enhanced thermodynamic stability, and this is usually demonstrated by relative heats of hydrogenation or heats of combustion measurements.
Indeed, once one understands the ortho-para and meta-directing character of these substituents, their directing influence on heterocyclic ring substitution is not difficult to predict.
Since its launch in 1973, Heterocycles has provided a platform for the rapid exchange of research in the areas of organic, pharmaceutical, analytical, and medicinal chemistry of heterocyclic compounds.
Heterocycles is owned and published by The Japan Institute of Heterocyclic Chemistry (www.heterocycles.com).
The distribution of Heterocycles outside Japan is handled by Elsevier.
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