Catechols

Catechols are a class of aromatic compounds based on a benzene ring bearing two hydroxyl groups in the adjacent (ortho) positions. The parent compound is catechol, also known as 1,2-dihydroxybenzene or pyrocatechol, with the formula C6H6O2. Substituents on the ring give a wide range of catechol derivatives.

Natural occurrence and significance: Catechol motifs are widespread in nature as subunits of polyphenols and other biomolecules. Examples include 3,4-dihydroxyphenylalanine (DOPA) and dopamine, which contain catechol groups within larger biological molecules. Catechols are common in plant polyphenols, lignin precursors, and pigments, and they play a key role in the adhesive chemistry of mussels, where catechol-containing proteins enable wet adhesion.

Chemical properties: Catechols are redox-active and readily oxidize to ortho-quinones. This oxidation can trigger polymerization, yielding melanin-like pigments, or participate in enzymatic reactions catalyzed by polyphenol oxidases such as tyrosinase. The dihydroxybenzene core can also chelate metal ions and act as nucleophiles in various reactions. The hydroxyl groups confer phenolic acidity and enable diverse chemical transformations.

Applications and distinction: In organic synthesis, catechols serve as versatile building blocks for polymers, ligands, dyes, and coatings. They are used in bioadhesives, pigments, and analytical chemistry as oxidative indicators. The term catechol should not be confused with catecholamines (for example, dopamine, epinephrine), which contain a catechol moiety but constitute a distinct class of biologically active molecules.