Synthesis of Fluorescein from Resorcinol and phthalic Acid
This fluorescent dye was first synthesized by Adolf von Baeyer in the 19th century. This is an acid catalysed reaction between resorcinol and phthalic anhydride.
Mechanism of Synthesis of Fluorescein from Resorcinol and Phthalic Acid
The following mechanism of the fluorescein synthesis was performed by von Baeyer involves mainly in two steps:
1. Friedel-Crafts Acylation and
2. Formation of Fluorescein.
Hydroxyl group of resorcinol acts as a nucleophile which attacks the carbonyl carbon of phthalic anhydride and forms an intermediate compound through electrophilic aromatic substitution. The reaction further proceeds through electrophilic substitutions that ultimately forms fluorescein. Presence of sulfuric acid in this synthesis increases the electrophilicity of phthalic anhydride.
