Binding Constant of Amines to Water/AOT/n-Hexene Reverse Micelles. Influence of the Chemical Structure

Abstract

Abstract:The distribution of different amines between n-hexane bulk and the micellar pseudophase of AOT reverse micelles were measured by a fluorometric method. An independent method was used to corroborate the incorporation of the amines to the interface. The effect of the amine structure on the binding constant was analysed.

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

“…On the other hand, the reported data are relevant for the quantitative description of processes involving amines as reactants and taking place in reverse micelles, such as the S N Ar [18][19][20][21] or aminolysistype reactions that have biological relevance [28,29]. Moreover, it is also showed that the studied amines are not protonated inside the (AOT)/n-hexane reverse micelles, which is a very interesting result dealing in reactivity of these substrates as nucleophiles [18][19][20][21]28,29].…”

“…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. To further check the possible influence of amine hydrolysis, K was measured for i-BA with the Ru(bpy) 2+ 3 -Fe(CN) 3− 6 at pH 12.…”

“…According to the pseudophase model, the partition constant K can be defined by [6,[18][19][20]30,31] (2)…”

“…In this work the distribution constants to water/AOT/ n-hexane reverse micellar pseudophase of different aliphatic and aromatic amines widely different in hydrophobicity and hydrogen bond donor abilities, such as n-butylamine (n-BA), isobutylamine (i-BA), tert-butylamine (t-BA), piperidine (PIP), N ,N -dimethylaniline (DMA) and N -methylaniline (MA), were determined concluding a preliminary report [23]. The constants were measured by an indirect method based on the effect that amine distribution exert on the bimolecular rate of the reaction between a microphase incorporated fluorophore (Ru(bpy) 2+ 3 ) and a quencher (Fe(CN) 3− 6 ) [24].…”

“…Moreover, in addition to the study of solubilization and properties of the interface in reverse micelles [4,[12][13][14][15][16][17], our group has been interested in the study of nucleophilic aromatic substitution (S N Ar) reactions between nitro-substituted aromatic substrates and aliphatic amines in different reverse micelles media [18][19][20][21]. The kinetic behavior was quantitatively explained taking into account the distribution of the substrate and the amines between the organic bulk solvents and the micellar interface, and the distribution constants of n-butylamine and piperidine were estimated from the kinetic data [18,20].…”