indophenol

Indophenol refers to a family of organic dyes that share the indophenol chromophore. The core structure is typically formed by the condensation of phenolic compounds with nitroaromatic partners under strongly basic conditions, producing blue or green dyes, of which indophenol blue is the best known.

Historically and chemically, indophenol dyes are produced by alkaline reactions that generate a highly conjugated chromophore capable of absorbing visible light. The most prominent application is the indophenol blue color produced in the Berthelot reaction, a colorimetric method for ammonia determination. In this method, ammonia is oxidized in alkaline solution by hypochlorite to form monochloramine, which then reacts with phenol to yield the blue indophenol dye. The resulting color intensity is proportional to ammonia concentration, allowing quantitative analysis.

Beyond ammonia testing, indophenol derivatives have served as textile dyes and as color reagents in various analytical methods, owing to their vivid coloration and redox-active properties. The specific properties and applications vary with substituents on the phenolic and nitroaromatic components, giving a range of hues and stabilities.

Safety and handling considerations are similar to other synthetic organic dyes: they should be used with appropriate protective equipment and disposed of according to regulations. References to specific dyes and procedures are found in analytical chemistry texts and dye chemistry literature.

See also: Berthelot reaction, indophenol blue.