L. Garcia-rio et Jr. Leis, Reactivity in quaternary water in oil microemulsions. 2. Different distribution of the reagents changing from three- to four-component microemulsions, J PHYS CH B, 104(28), 2000, pp. 6618-6625
A study was carried out on the nitrosation of piperazine (PIP) and N-methyl
benzylamine (MeBzAm) by N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) at 2
5 degrees C in quaternary tetradecyltrimcthylamnlonium bromide (TTABr)/1 -h
exanol/isooctane/water microemulsions, ensuring that the relationship [1-he
xanol]/[TTABr] = 4 remained constant. In order to interpret the experimenta
l results, we extended the formalism of the micellar pseudophase to microem
ulsions thereby considering the distribution of the alcohol throughout the
pseudophases of the microemulsion and the change in the volume of the inter
face. The volume of the interface, calculated from the molar volumes of the
surfactant and the alcohol, was included in the kinetic model to quantify
the dilution of the reagents associated at the interface. The application o
f the developed kinetic model to the two systems studied has shown that the
presence of alcohol in the continuous medium increases its hydrophilicity.
Hence, unlike in the case of the tertiary AOT/isooctane/water microemulsio
ns, it is necessary to bear in mind that the piperazine is distributed betw
een the three pseudophases of the microemulsion. A comparison of the result
s obtained in TTABr/1-hexanol/isooctane/water microemulsions with those of
AOT/isooctane/water shows that the incorporation of the alcohol into the in
terface increases its hydrophobicity by displacing water molecules and henc
e reducing the bimolecular rate constant for the reaction at the interface.