Upon completion of this module, you should be able to understand the classification of organic compounds and distinguish between these compounds: acyclic, homocyclic, heterocyclic, alicyclic, aromatic, and benzenoid. Organic compounds are classified into various categories depending on the structure of the molecule. Organic Compounds are divided into two major categories: Open Chain / Acyclic and Closed Chain / Cyclic compounds. A compound that contains an open chain of carbon atoms is acyclic. For open-chain compounds, the ends of the molecule do not connect to form a ring.