A Three-Step Synthesis of Para Red

A Three-Step Synthesis of Para Red

Samantha Geissler, Shannon Brick

A three step synthesis was done to form Para Red. Para Red is used for dying cellulose fabricsa bright red, but it can be washed away easily if not dyed correctly. Aniline was used as the starting material to execute nucleophilic addition-elimination with acetic anhydride to form acetanilide. Acetanilide was subsequently nitrated and hydrolyzed to form p-nitroaniline. NaNO₂ was then added to the p-nitroaniline to form a diazonium salt, which was subjected to an azo coupling reaction to form Para Red. To make the reaction greener, HCl was used in place of H₂SO₄ in step two because HCl is safer than sulfuric acid because it is less reactive. HCl is normally stable but could become unstable at high pressures where sulfuric acid could form explosive mixtures when it reacts with water. The Para Red produced in this scheme was tested on a series of fabrics: cotton, silk, and polyester to test its dying properties.