Pseudophase Approach to Reactivity in Microemulsions:  Quantitative Explanation of the Kinetics of the Nitrosation of Amines by Alkyl Nitrites in AOT/Isooctane/Water Microemulsions

Abstract

The kinetics of nitroso group transfer from 2-ethoxyethyl (EEN) and 2-bromoethyl (BEN) nitrite to the secondary amines piperazine (PIP), N-methylbenzylamine (NMBA), and morpholine (MOR) in bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane (iC8)/water microemulsions were determined. They are explained quantitatively in terms of a model in which the reagents are distributed among the aqueous, organic, and AOT film surfactant, with the aqueous pseudophase and the surfactant film as the loci of the reaction.

Microheterogeneous Solvation for Aminolysis Reactions in AOT‐Based Water‐in‐Oil Microemulsions

“…In our research group a kinetic model has been developed, based on the formalism of the pseudophase which can be applied to inter- pret quantitatively the influence of the composition of the microemulsion on the chemical reactivity. [29,30] As is usual on studying reactivity in colloidal systems (micelles, vesicles and microemulsions) the activity coefficients of the components in these systems are independent of their concentrations. To apply this formalism to the aminolysis of the NPA we must consider the microemulsion formed by three strongly differentiated pseudophases: [31] an aqueous pseudophase (w), a continuous medium formed fundamentally by the isooctane (o) and an interface formed fundamentally by the surfactant (i).…”

Distribution of amines in water/AOT/n-hexane reverse micelles: influence of the amine chemical structure

“…Thus, it could be argued that hydrolysis can occur with aliphatic amines in AOT aqueous reverse micellar systems. However, no hydrolysis had been detected for previously studied S N Ar reactions of aliphatic amines with halo-nitrobenzene compounds in water/AOT/ n-hexane [18][19][20] or in reaction of nitrosation of amines in water/AOT/isooctane [28,34]. Moreover, the partition constants obtained in this work for n-BA and PIP are coherent with the values previously calculated from kinetic data for the S N Ar reaction with 1-chloro-2,4-dinitrobenzene [19] and 1-fluoro-2,4-dinitrobenzene [18,20] in the same reverse micellar system.…”

The dependence of micellar rate effects upon reaction mechanism

“…However, the role of "local concentration" is exemplified by the very large rate enhancements of bimolecular reactions of hydrophilic, ionic, reactants by reverse micelles, where concentration in the aqueous microdroplets is all important, and very much higher than that in terms of the total solution volume [36,37].…”