In my work for a bachelor’s degree, the isomers of 4'-carboxy- and 5'-carboxyrhodamine B 3a/3b were synthesized and methods for their separation were investigated. The synthesis was performed from 1,2,4-benzenetricarboxylic anhydride and 3-(diethylamino)phenol. Following the extraction of the product from the reaction mixture, various methods were employed in an attempt to separate the resulting mixture of isomers: column chromatography, medium pressure liquid chromatography (MPLC) and preparative thin-layer chromatography. Despite multiple attempts with different chromatographic methods, the separation was initially unsuccessful. However, the use of preparative thin-layer chromatography proved effective in separating the isomers. The identification of isomers 3a and 3b was carried out using NMR, infrared spectroscopy, ultraviolet-visible spectroscopy, emission spectroscopy and mass spectrometry. These results were then compared with existing literature data. The separation was successfully achieved and the isomers of carboxyrhodamine B were characterized.
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