Aromatization

Aromatization is a chemical process that forms an aromatic ring system in a molecule or converts a non-aromatic compound into an aromatic one. Aromatic systems are typically planar, cyclic, and fully conjugated, with a closed loop of pi electrons obeying Hückel's rule (4n+2). The resulting compounds, often called aromatics, are unusually stable relative to non-aromatic precursors.

In organic synthesis, aromatization can occur by dehydrogenation (loss of hydrogen), oxidation, or intramolecular cyclization and rearrangement that yields a fully conjugated, six-membered ring or polycyclic ring system. Common routes include dehydrogenation of cyclohexadienes to benzene, and cyclodehydrogenation forming polycyclic aromatics such as naphthalene and phenanthrene. Catalysis and reaction conditions influence the mechanism and selectivity.

In biochemistry, aromatization refers to enzyme-catalyzed formation of an aromatic A-ring in steroid hormones, most notably the conversion of androgens (testosterone, androstenedione) to estrogens (estradiol, estrone) by the enzyme aromatase (cytochrome P450 19A). This reaction adds three double bonds, creating an aromatic ring in the steroid framework.

In geology and industry, aromatization can describe the thermal maturation of organic matter, producing aromatic hydrocarbons from aliphatic precursors under heat. Aromatization reactions are important in petrochemical processing and in the synthesis of dyes, polymers, and pharmaceuticals where stable aromatic motifs are desired.