Heterocyclic Compounds Heterocyclic compounds are cyclic compounds in which the ring contains at least one atom of an element other than carbon. In homogeneous cyclic compounds such as benzene, all the atoms that make up the ring are of one type, so they are called homocyclic compounds, and few Non-carbon elements are capable of forming homogeneous rings, and examples of heterocyclic compounds that do not contain the carbon element Pentamethyl-Pentaristol When the cyclic structure contains atoms of different elements, these compounds are known as heterocyclic compounds. Often such compounds contain carbon atoms with one or more other elements. The most common of these elements are oxygen, nitrogen, sulfur, and less commonly. The elements mercury, arsenic, lead, phosphorous and other elements are included, as shown in Figure (2-1) ((1). Figure 1-2: Some heterocyclic compounds