Question

These are three structures of the dye phenolphthalein which of these is

responsible for the characteristic pink colour and why? Also relate the structures

with the pH?​

Answer 1

Phenolphthalein (pronounced fee-nawl-thal-een), often abbreviated to phph, is a weak acid. This mildly acidic compound is a white to yellow crystalline solid. It easily dissolves in alcohols and is slightly soluble in water. Phenolphthalein is a large organic molecule with the chemical formula of C20H14O4.

The phenolphthalein indicator allows chemists to visually identify whether a substance is an acid or a base. The color change in phenolphthalein is a result of ionization, and this alters the shape of the phenolphthalein molecules.