Compared with classical experimental design of tautomerism based on NMR technology, it is believed that convenient, interesting, and colorful experimental design will be popular among students. In this work, the classical keto–enol tautomerization was introduced into common organic dyes (naphthalimides) as key experimental reagents. Three prototropic tautomer experimental reagents based on a naphthalimide chromophore were designed and prepared. During the experiment, students were able to intuitively observe the occurrence of tautomerization by visualizing changes in color and UV–vis spectra. By comparing the color and spectral characteristics of three preset molecules in different polar solvents, students were made aware of the structural and environmental factors that affected the occurrence of tautomerism and the law of isomerization.
Lan et al. (Mon,) studied this question.