The Comparative Nucleophilicity of Naphthoxide Derivatives in Reactions with a Fast-Red TR Dye

摘要

In this experiment, organic chemistry students perform reactions between three naphthyl acetate derivatives and the diazonium salt Fast-Red TR, under basic conditions. The three naphthyl acetate derivatives used in this study are 2-naphthyl acetate (1a), 6-bromo-2-naphthyl acetate (1b) and 1,6-dibromo-2-naphthyl acetate (1c). The two-step, one-pot reactions (ester hydrolysis followed by reaction with Fast Red TR) are screened for the formation of an orange–red diazo dye both visually and by UV–vis spectroscopy. Students discover that the hydrolysis and electrophilic aromatic substitution is the fastest with ester 1a and the slowest with ester 1c. This allows students to conclude that electrophilic aromatic substitution, rather than ester hydrolysis, is rate-limiting. This experiment is performed over a two-week period: during the first week students synthesize and purify compounds 1b and 1c, which are easily characterized through 1H NMR and IR spectroscopies. The ester hydrolysis and diazotization visual and UV–vis studies are performed during the second week of the experiment.