The preparation of a fluorescent dye: a microscale TLC experiment

A thin-layer chromatography (TLC) microscale experiment based on synthesis of a fluorescent dye has been developed. Synthesis of the very fluorescent dye, 4-hexylamino-N-hexyl-1,8-naphthalimide, from technical grade 4-chloro-1,8-naphthalic anhydride is carried out. The experiment has qualities that will excite the imagination of typical undergraduate chemistry students. Students can monitor the progress of the reaction using TLC and will respond more positively than they will to most exercises involving TLC, most of which involve visualization effected by charge-transfer complexation with iodine or by looking at fluorescence quenching of an inorganic fluorescer added to adsorbent.