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Decarboxylation of 6-Nitrobenzisoxazole-3-carboxylate in Mixed Micelles of Zwitterionic and Positively Charged Surfactants

Maximiano, Flavio A ; Chaimovich, Hernan ; Cuccovia, Iolanda M

Langmuir, 2006-09, Vol.22 (19), p.8050-8055 [Periódico revisado por pares]

Washington, DC: American Chemical Society

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  • Título:
    Decarboxylation of 6-Nitrobenzisoxazole-3-carboxylate in Mixed Micelles of Zwitterionic and Positively Charged Surfactants
  • Autor: Maximiano, Flavio A ; Chaimovich, Hernan ; Cuccovia, Iolanda M
  • Assuntos: Catalysis ; Chemistry ; Colloidal state and disperse state ; Exact sciences and technology ; General and physical chemistry ; Micelles. Thin films ; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
  • É parte de: Langmuir, 2006-09, Vol.22 (19), p.8050-8055
  • Notas: istex:C752435311D8FC009774F034811EA07CDAA6F632
    ark:/67375/TPS-RCZ0GT4K-1
    ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
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  • Descrição: The rate of decarboxylation of 6-nitrobenzisoxazole-3-carboxylate, NBOC, was determined in micelles of N-hexadecyl-N,N,N-trimethylammonium bromide or chloride (CTAB or CTAC), N-hexadecyl-N,N-dimethyl-3-ammonium-1-propanesulfonate (HPS), N-dodecyl-N,N-dimethyl-3-ammonium-1-propanesulfonate (DPS), N-dodecyl-N,N,N-trimethylammonium bromide (DTAB), hexadecylphosphocholine (HPC), and their mixtures. Quantitative analysis of the effect on micelles on the velocity of NBOC decarboxylation allowed the estimation of the rate constants in the micellar pseudophase, k m, for the pure surfactants and their mixtures. The extent of micellar catalysis for NBOC decarboxylation, expressed as the ratio k m/k w, where k w is the rate constant in water, varied from 240 for HPS to 62 for HPC. With HPS or DPS, k m decreased linearly with CTAB(C) mole fraction, suggesting ideal mixing. With HPC, k m increased to a maximum at a CTAB(C) mole fraction of ca. 0.5 and then decreased at higher CTAB(C). Addition of CTAB(C) to HPC, where the negative charge of the surfactant is close to the hydrophobic core, produces tight ion pairs at the interface and, consequently, decreases interfacial water contents. Interfacial dehydration at the surface in equimolar HPC/CTAB(C) mixtures, and interfacial solubilization site of the substrate, can explain the observed catalytic synergy, since the rate of NBOC decarboxylation increases markedly with the decrease in hydrogen bonding to the carboxylate group.
  • Editor: Washington, DC: American Chemical Society
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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