Fenoliftaleeni

Fenolftaleeni, also known as phenolphthalein, is a chemical compound with the formula C20H14O4. It is a white to yellowish-white crystalline powder. Fenolftaleeni is a weak acid and is insoluble in water but soluble in ethanol and ether.

The most common application of fenolftaleeni is as a pH indicator in acid-base titrations. In acidic solutions, it remains colorless. As the solution becomes alkaline, fenolftaleeni undergoes a structural change, transitioning to a pink or fuchsia color. This color change typically occurs in the pH range of 8.2 to 10.0, making it useful for determining the endpoint of titrations involving strong bases and weak acids, or strong acids and weak bases.

Historically, fenolftaleeni was also used as a laxative. However, due to concerns about its potential carcinogenicity, this use has largely been discontinued in many countries. Research has indicated a link between long-term, high-dose exposure and tumor formation in rodents. Consequently, many over-the-counter laxative products now use alternative active ingredients.

Fenolftaleeni can be synthesized through the reaction of phthalic anhydride with phenol in the presence of a dehydrating agent like sulfuric acid. It is a relatively stable compound under normal conditions. Its distinct color change mechanism is due to the ionization of its phenolic hydroxyl groups, leading to a change in its conjugated system and thus its absorption of visible light.