fenoliftaleiinin

Phenolphthalein is a chemical compound with the formula C20H14O4. It is often used as an acid-base indicator due to its distinct color change in solution. In acidic conditions, phenolphthalein is colorless. As the pH of the solution increases and becomes alkaline, phenolphthalein undergoes a structural change and turns a vibrant pink or fuchsia color. This color change typically occurs within a pH range of approximately 8.2 to 10.0.

The chemical structure of phenolphthalein consists of two phenol rings attached to a central lactone ring. Its synthesis typically involves the reaction of phenol with phthalic anhydride in the presence of an acid catalyst. Historically, phenolphthalein was widely used as a laxative, but concerns about its potential carcinogenicity led to its removal from many over-the-counter medications in several countries. Today, its primary use remains in analytical chemistry as a pH indicator, particularly in titrations to determine the endpoint of acid-base reactions. It is also sometimes incorporated into novelty items like disappearing inks due to its pH-dependent color.