It is known that when pH of solution is greater than 12 phph solution turns colorless. And the structural change which occurs is I want to ask why OH_ group attack sp2 hybridized carbon atom attached to three different rings? How elecrophilic site is generated there? In one of its bonding orbitals it contains phenoxide ion bonded through para position which is supposed to be electron rich site. Wouldn't this bonding sway positive charge created by adjacent benezecarboxalate ion bonded to carbon through ortho postion?