Abstract
The condensation of the halogeno substitutes of 2-(2′, 4′-dihydroxybenzoyl) benzoic acid (II), derived from the decomposition of either chloro or bromo-fluorescein (I) in concentrated NaOH solution, and either resorcinol or its halogeno derivatives (III), afforded a new chloro-bromo mixed substituted fluorescein (IV), shown in Table I. When polyphosphoric acid was used as a condensation agent in the reaction, a debromination reaction scarecely took place, and a yield of IV was poor. If the condensation was proceeded at 120-150° in the presence of ZnCl2, a yield of IV was pretty rich, even though debromination reaction was accompanied, and the less number of halogeno substitute (IV) was produced subordinately. A little amount of by-products can be removed by treating them in ethanolic HCl, however, a comparatively larger amount of by-products should be separated through the column chromatography of alumina or magnesol, being followed by the elution with 2-3% NH4OH.
The production of by-product can be easily identified by the paperchromatography, developed by the solvent mixture of N NaOH-10% C6H5OH-H2O (2:1:7).
