Ghoneim, M. M. published the artcileInfrared spectra of some derivatives of phenolphthalein and sulfonphthalein, Application In Synthesis of 596-01-0, the publication is Indian Journal of Chemistry, Section A: Inorganic, Physical, Theoretical & Analytical (1979), 18A(4), 349-50, database is CAplus.
The comparison of the IR of phenolphthalein, sulfonphthalein and their derivatives, observed in KBr, indicates that the phenolphthaleins exist mainly in the lactone form; sulfonphthaleins have the quinone-like structure. This behavior is attributed to the higher tendency of sulfonphthalein to form the sulfonate ion than the phenolphthalein to attain the carboxylic structure.
Indian Journal of Chemistry, Section A: Inorganic, Physical, Theoretical & Analytical published new progress about 596-01-0. 596-01-0 belongs to benzofurans, auxiliary class Benzofuran,Naphthalene,Alcohol,Ester, name is 3,3-Bis(4-hydroxynaphthalen-1-yl)isobenzofuran-1(3H)-one, and the molecular formula is C28H18O4, Application In Synthesis of 596-01-0.
Referemce:
https://en.wikipedia.org/wiki/Benzofuran,
Benzofuran | C8H6O – PubChem