orthohydroxybenzoic

Ortho-hydroxybenzoic acid, commonly known as 2-hydroxybenzoic acid or salicylic acid, is an organic compound with the formula C7H6O3. It features a benzene ring bearing adjacent hydroxyl and carboxyl substituents (an ortho relationship).

Salicylic acid is a white crystalline solid with a melting point around 158–161°C. It is sparingly soluble in water but dissolves in many organic solvents such as ethanol, acetone, and diethyl ether. The molecule can form intramolecular hydrogen bonds, influencing its acidity and solubility. The carboxyl group is the primary acidic site (pKa about 2.97); the phenolic hydroxyl has a much higher pKa, around 13.

Natural occurrence and role: Salicylic acid occurs in several plants, notably willow bark, and is involved in plant defense signaling. In pharmacology and medicine, it is a key precursor to aspirin (acetylsalicylic acid) and is used for its keratolytic and anti-inflammatory properties in dermatology and cosmetic formulations.

Chemistry and production: Industrially, salicylic acid is often prepared by Kolbe-Schmitt-type carboxylation of sodium phenoxide with carbon dioxide to yield sodium salicylate, which is acidified to the free acid. It can also be obtained by hydrolysis of acetylsalicylic acid or via other synthetic routes. In laboratories, salicylic acid serves as a standard reference material and a versatile starting point for esters and ethers used in pharmaceuticals and cosmetics.

Safety: Salicylic acid can irritate skin and mucous membranes; larger doses may cause salicylate toxicity. It is handled as a chemical intermediate with appropriate safety measures and disposal practices.