The properties of water solubilized by cetyltripropylammonium bromide (CTPABr) and sodium bis 2-ethylhexyl)sulfosuccinate (AOT) in CCl4 were studied as a function of the number of water molecules per surfactant molecule (W) by the kinetics of decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate ion (6NBIC) and IR spectroscopy in the O-H stretching region in the region of low water (0 < W < 10) where the properties depend strongly upon W. Decarboxylation of 6NBIC in CTPABr reverse micelles is strongly inhibited by an increase in W and the first-order constants level o at W > 1. The rate e ects are ascribed to increases in polarity and hydrogen bonding in the reaction region as water is added and are related to changes in the IR spec- trum. For the AOT system, the kinetics is independent of W and this difference from the behaviour of the CTPABr system is ascribed to the difference in the interactions of 6NBIC with surfactant headgroups.
Relation between the IR Spectrum of Water and Decarboxylation Kinetics in Microemulsions
GERMANI, Raimondo;ONORI, Giuseppe;SANTUCCI, Aldo;
2001
Abstract
The properties of water solubilized by cetyltripropylammonium bromide (CTPABr) and sodium bis 2-ethylhexyl)sulfosuccinate (AOT) in CCl4 were studied as a function of the number of water molecules per surfactant molecule (W) by the kinetics of decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate ion (6NBIC) and IR spectroscopy in the O-H stretching region in the region of low water (0 < W < 10) where the properties depend strongly upon W. Decarboxylation of 6NBIC in CTPABr reverse micelles is strongly inhibited by an increase in W and the first-order constants level o at W > 1. The rate e ects are ascribed to increases in polarity and hydrogen bonding in the reaction region as water is added and are related to changes in the IR spec- trum. For the AOT system, the kinetics is independent of W and this difference from the behaviour of the CTPABr system is ascribed to the difference in the interactions of 6NBIC with surfactant headgroups.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
