2-((4-Hydroxyphenyl)(4-oxo-2,5-cyclohexadien-1-ylidene)methyl)benzoic acid 5768-87-6 Benzoic acid, 2-((4-hydroxyphenyl)(4-oxo-2,5-cyclohexadien-1-ylidene)methyl)- Phenolphthalein o-Toluic acid, alpha-(p-hydroxyphenyl)-alpha-4-oxo-2,5-cyclohexadien-1-ylidene-