Diphenolic acid is a carboxylic acid with molecular formula C17H18O4. Its IUPAC name is 4,4-bis(p-hydroxyphenyl)pentanoic acid, and it can be prepared by the condensation reaction of phenol with levulinic acid in the presence of hydrochloric acid. The equation for this synthesis is:
2 C6H5OH + CH3C(O)CH2CH2COOH CH3C(p-C6H4OH)2CH2CH2COOH + H2O
Diphenolic acid is a solid at room temperature, melting at 168171C and boiling at 507C.