Inhibited Phenol Ionization in Reverse Micelles: Confinement Effect at the Nanometer Scale

O FERNANDO SILVA; MARIANA A. FERNÁNDEZ; JUANA J. SILBER; RITA H. DE ROSSI; N. MARIANO CORREA

WILEY-V C H VERLAG GMBH

Año: 2012 vol. 13 p. 124 - 124

e found that the absorption spectra of 2-acetylphenol (2-HAP), 4-acetylphenol (4-HAP), and p-nitrophenol (p-NPh) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane reverse micelles (RMs) at various W0 (W0=[H2O]/[surfactant]) values studied changed with time if <M->OH ions were present in the RM water pool. There is an evolution of ionized phenol (phenolate) bands to nonionized phenol absorption bands with time and this process is faster at low W0 values and with phenols with higher bulk water pKa values. That is, in bulk water and at the hydroxide anion concentration used, only phenolate species are observed, whereas in AOT RMs at this fixed hydroxide anion concentration, ionized phenols convert into nonionized phenol species over time. Furthermore, we demonstrate that, independent of the <M->OH concentration used to prepare the AOT RMs, the nonionized phenols are the more stable species in the RM media. We explain our results by considering that strong hy