PARA-HYDROXYBENZOIC ACID (PHBA), also known as 4-Hydroxybenzoic acid, is a phenolic derivative of benzoic acid. It is a solid that appears in a white crystal form. Its solubility in water is very small, however it is easily soluble in polar organic solvents such as alcohols and acetone. It is considered to be a precursor for other acids (mostly phenolic acids) in chemical reactions.
Para-hydroxybenzoic acid is manufactured commercially from the Kolbe-Schmitt reaction of potassium phenoxide and carbon dioxide. Another way of its production is to heat potassium salicylate with potassium carbonate to 240 °C, and later treat the substance with acid.
In the medical industry, para-hydroxybenzoic acid is used in the production of aspirin. It is a precursor of salicylic acid which is the basic component of this medicine.
In the cosmetic and pharmaceutical industries it is used to prepare preservatives (mostly parabens) for shampoos, commercial moisturizers, shaving gels, pharmaceuticals, personal lubricants, spray tanning solutions, and toothpaste.