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

Autor(es)

Reis, Roberta Albino ^[1] ; Boaro, Andreia ^[1] ; Orfao, Ronaldo Barros ^[1] ; Melo, Diego Ulysses ^[1] ; Bartoloni, Fernando Heering ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed ABC, Ctr Ciencias Nat & Humanas, BR-09210580 Santo Andre, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: LUMINESCENCE; v. 34, n. 2, p. 234-242, MAR 2019.
• Citações Web of Science: 0

Resumo

The kinetics of the decomposition reaction of 4-(4,5-diphenyl-1H-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 (phi(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 (lambda(ex) = 300 nm, lambda(em) = 400 nm) or product formation (lambda(ex) = 350 nm, lambda(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 (iPrOH), upon addition of HO-, provided evidence that the solvent's conjugate base is the active nucleophilic species. When different bases were used (tBuO(-), 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 pK(aH), suggesting specific base catalysis for the decomposition of 1 in alcoholic media. (AU)

• Processo FAPESP: 12/13807-7 - Novas ferramentas para o estudo de reações de transferência de elétron em sistemas modelo do PS II
• Beneficiário: Fernando Heering Bartoloni
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/05813-2 - Aplicação de fluoróforos contendo grupos fenólicos e nitrogenados na detecção de metais por emissão de luz
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• Processo FAPESP: 16/10585-4 - Aspectos mecanísticos da decomposição induzida de hidroperóxidos e sililperóxidos derivados de lofina
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