Diazonaphthoquinone-5-sulfonate composition variants: synthesis and properties

The influence of reaction variables on the formation of polyhydroxybenzene diazonaphthoquinone sulfonate esters was investigated. Solvent polarity, base, reactant concentration and reaction temperature were all found to have large effects. High solvent polarity was observed to promote formation of highly esterified products. The condensation of 2,3,4-trihydroxybenzophenone with diazonaphthoquinone sulfonyl chloride in dimethylacetamide or N-methyl-2-pyrrolidone resulted in a diester isomer distribution that was different than that observed in acetone, 1,4-dioxane, methyl ethyl ketone, tetrahydrofuran and gamma-butyrolactone. Further, the initial sulfonate esters were formed under kinetic control. In the presence of base and 2,3,4-trihydroxybenzophenone the esters equilibrated to form a common, thermodynamically favored mixture. The equilibration rate was fast in solvents having high polarity. An equilibration scheme is proposed involving phenolate ion displacement processes.