mechanism for phenolphthalein from 2 phenol molecules and phthalic anhydrided?

Answer 1

The reaction is initiated by ZnCl2 or H2SO4. You can look up the structure of phthalic anhydride. The important part is one of the O-C=O's of phthalic anhydride. That O gets protonated, the ring opens, and next there is a (+)C=O hanging loose. That (+) attacks phenol (twice!) in nucleophilic aromatic sudstitution, which produces a (C6H4-OH)2 attached to the lactone of the newly formed phenolphthalein. The acid-base reaction (red-white) reaction results from the opening and closing of the lactone ring.

Answer 2

Synthesis Of Phenolphthalein