The decomposition of triphenylimidazole‐ para ‐acetate follows specific base catalysis and can be conveniently followed by fluorescence

The kinetics of the decomposition reaction of 4‐(4,5‐diphenyl‐1 H ‐imidazol‐2‐yl)phenyl acetate ( 1 ) in basic alcoholic media was investigated, using a simple fluorescence (FL) spectrophotometric procedure. The process was conveniently studied using FL, since the triphenylimidazole‐derived ester 1 and its reaction products (the corresponding phenol 2 and phenolate 2 − ) are all highly fluorescent (Φ FL  > 37%). By carefully selecting excitation and emission wavelengths, observed rate constants k 1 in the order of 10 −3 to 10 −2  s −1 were obtained from either reactant consumption ( λ ex  = 300 nm, λ em  = 400 nm) or product formation ( λ ex  = 350 nm, λ em  = 475 nm); these were shown to be kinetically equivalent. Intensity‐decay time profiles also gave a residual FL intensity parameter, shown to be associated to the distribution of produced species 2 and 2 − , according to the basicity of the medium. Studying the reaction in both methanol (MeOH) and isopropanol ( i PrOH), upon addition of HO − , provided evidence that the solvent's conjugate base is the active nucleophilic species. When different bases were used ( t BuO − , HO − , DBU and TEA), bimolecular rate constants k bim ranging from 4.5 to 6.5 L mol −1  s −1 were obtained, which proved to be non‐dependent on the base p K aH , suggesting specific base catalysis for the decomposition of 1 in alcoholic media.