Investigation of the Colour Reaction of Resorcinols with Nitrous Acid. Spectrophotometric Determination of Resorcinol, 4-n-Hexylresorcinol and 2,4,6-Tribromoresorcinol

Jiří Gasparič (gasparic@faf.cuni.cz)

Department of Biophysics and Physical Chemistry, Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Czech Republic

Summary

Five modifications of the colour reaction of resorcinol with nitrous acid in acidic media were studied. The coloured reaction products, i. e. dinitrosoresorcinol, its Na salt or alkali salts of nitroresorcinols are formed depending on the reaction conditions used (temperature, acid and reagent concentration, reaction time, substituents). The most sensitive photometric procedure is that resulting in the formation of the Na salt of 2,4-dinitrosoresorcinol, procedures in which alkali salts of 2,4,6-trinitroresorcinol are formed are less accurate. The reaction course and chromogens in the case of 4-n-hexyl- and 2,4,6-tribromoresorcinols were also investigated.