Heterocyclic compounds are organic compounds containing at least one atom of carbon, and at least one element other than carbon, such as sulfur, oxygen or nitrogen within a ring structure. These structures may comprise either simple aromatic rings or non-aromatic rings. Some examples are pyridine (C5H5N), pyrimidine (C4H4N2) and dioxane (C4H8O2). Note that compounds such as cyclopropane, an anaesthetic with explosive properties, and cyclohexane, a solvent, aren't heterocyclic; they're cycloalka… (More on Heterocycle)