Diphenolic acid is a carboxylic acid with molecular formula C<sub>17</sub>H<sub>18</sub>O<sub>4</sub>. Its IUPAC name is 4,4-bis(4-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 C<sub>6</sub>H<sub>5</sub>OH + CH<sub>3</sub>C(O)CH<sub>2</sub>CH<sub>2</sub>COOH â CH<sub>3</sub>C(p-C<sub>6</sub>H<sub>4</sub>OH)<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>COOH + H<sub>2</sub>O
Diphenolic acid is a solid at room temperature, melting at 168âÂÂ171 ðC and boiling at 507 ðC. 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 diglycidyl ether of bisphenol A.The diglycidyl ethers of n-alkyl diphenolate esters have similar thermomechanical properties to the diglycidyl 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.