The question of the fixation of the aromatic double bonds in hydroxy-chromones and coumarins. Formation of azo-dyes

Abstract

The formation of azo-dyes using one and more than two molecular proportions of diazotised p-nitraniline and the following compounds has been investigated: (1) 2-methyl-3-methoxy-7-hydroxychromone, (2) 7-hydroxyflavone, (3) 7-hydroxycoumarin and (4) 4-methyl-7-hydroxycoumarin. (I) yielded a bis-azo dye with two molecules of the reagent and with one molecule of it a large proportion of the same bis-azo dye contaminated with the mono-azo compound. The other three behaved alike yielding mono-azo dyes with one molecule of the reagent and the same mono-azo compound predominantly mixed with considerable amounts of the bis-compounds when more than two molecular proportions of the reagent were employed. The factors controlling the composition of the azo-dyes that are formed seem to be very complex.