Diphenolic acid

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 168–171 °C and boiling at 507 °C. According to its MSDS, diphenolic acid is soluble in ethanol, isopropanol, acetone, acetic acid, and methyl ethyl ketone, but insoluble in benzene, carbon tetrachloride, and xylene.

Diphenolic acid may be a suitable replacement for bisphenol A as a plasticizer.

Diphenolate esters have been used to synthesize epoxy resins as a replacement for the digylcidyl ether of bisphenol A.The digylcidyl ethers of n-alkyl diphenolate esters have similar thermomechanical properties to the digylcidyl ether of bisphenol A when cured, but the viscosity and glass transition temperature vary as a function of the ester length. Diphenolate esters have also been used to synthesize polycarbonates with a potential for water solubility.