Heterocyclic synonyms

Carbocyclic rings will next be treated, benzene and its allies in some detail; and finally the heterocyclic nuclei.

In classifying closed chain compounds, the first step consists in dividing them into: (1) carbocyclic, in which the ring is composed solely of carbon atoms - these are also known as homocyclic or isocyclic on account of the identity of the members of the ring - and (2) heterocyclic, in which different elements go to make up the ring.

and >- CH, the first characterizing the polymethylene and reduced heterocyclic compounds, the second true aromatic compounds.

The elements which go to form heterocyclic rings, in addition to carbon, are oxygen, sulphur, selenium and nitrogen.

Thus ortho-phenylene diamine yields the following products: N H N ./`N; Xn NZ In some cases oxidation of condensed benzenoid-heterocyclic nuclei results in the rupture of the heterocyclic ring with the formation of a benzene dicarboxylic acid; but if the aromatic nucleus be weakened by the introduction of an amino group, then it is the benzenoid nucleus which is destroyed and a dicarboxylic acid of the heterocyclic ring system obtained.