phenolftaleiini

Phenolphthalein is a chemical compound with the formula C20H14O4. It is an organic compound belonging to the class of phthalide dyes. Phenolphthalein is commonly known for its use as a pH indicator. In acidic solutions, it is colorless. However, as the pH increases and becomes alkaline, phenolphthalein undergoes a structural change that causes it to turn pink or fuchsia. This color change occurs within a specific pH range, typically between 8.2 and 10.0, making it useful for titrations involving weak acids and strong bases, or strong acids and strong bases.

Beyond its role as an indicator, phenolphthalein was historically used as a laxative. Its effectiveness as a stimulant laxative was due to its ability to irritate the intestinal lining, promoting bowel movements. However, due to concerns about its potential carcinogenicity, it has been largely withdrawn from over-the-counter laxative preparations in many countries. Despite this, it remains widely used in laboratories for chemical analysis and educational demonstrations. Its synthesis involves the reaction of phenol with phthalic anhydride in the presence of an acid catalyst.