The solubilization of octylamidotartaric acid (C8T) and octanoic acid (C8C) in Triton X-100 and Brij 58 nonionic micelles has been studied by pHmetric and 1H NMR self-diffusion experiments. As both C8C and C8T exhibit acid-base properties, a distinction between the partition of the neutral acidic form, in terms of the partition coefficient KPH, and the partition of the charged basic form, in terms of the partition coefficient KP-, has been made. The acidity constants, Ka, of C8T and C8C in the presence of micelles have been evaluated from pHmetric experiments. For both solutes, an increase in the pKa is observed in micellar media due to the difference in the partition of acidic and basic forms of the solutes. A model has been developed to determine KPH and KP- from the pKa shifts observed. The values obtained by this pKa shift modeling method and those from self-diffusion coefficient measurements are in good agreement. The acidic form of C8C is incorporated to a larger extent into the Brij 58 micelles than the acidic form of C8T, whereas the opposite trend is observed for the basic forms. Both the acidic and basic forms of C8T are more easily incorporated into Brij 58 micelles than into Triton X-100 micelles. The influence of the structure of the polar head on the solubilization properties is demonstrated. Moreover, evidence for the localization of the solutes in the micelles is obtained from the comparison of the partition coefficients and from 1H NMR data.

The complexation of Cu(II) with original alkylamidotartaric acids (C(x)T) is investigated in homogeneous aqueous medium and in the presence of nonionic micelles of Brij 58 (C16EO20), thanks to various analytical techniques such as NMR self-diffusion experiments, CD and UV-vis spectroscopy, ESI mass spectrometry, pHmetry and micellar-enhanced ultrafiltration (MEUF). First, a complete speciation study proves the formation of dimeric complexes in water and provides their formation constants. Second, a similar study is led in the presence of nonionic micelles. It underlines a modification of the apparent equilibrium constants in micellar medium and demonstrates that the structure of the complexes is slightly modified in the presence of micelles. This thermodynamic and structural study is applied to modelize the evolution of the extraction yields of Cu(II) by the micelles as a function of pH and to identify the complexes extracted in the micelles. The effects of the chain length of the ligand (C3T vs C8T) on the solubilization properties are put into relief and discussed. Anionic species are proved to be more incorporated in the nonionic micelles than the cationic species. The extracting system constituted of octylamidotartaric acid (CsT) solubilized in nonionic micelles of Brij 58 is demonstrated to be very efficient for the extraction of Cu(II) by MEUF, this technique being an interesting green alternative to traditional solvent extraction.

The surfaces of proteins and membranes are dotted with a multitude of proton binding sites, some of which are only a few tenths of a nanometer apart. This proximity between proton binding sites could be at the origin of the fast proton transfers occurring at the biological scale.[1] In order to understand this phenomenon more precisely, we investigated the mechanism of proton transfer at the surface of cationic micelles composed of amphiphilic ammonium chloride salts. Proton transfer rates were obtained from the overall analysis of the DNMR (dynamic nuclear magnetic resonance) signals in experiments varying the pH and the salt concentrations of aqueous solutions at 25 8C.[2-4] Exchange rates of the acidic proton of amphiphilic ammonium salts BH+ with R = n-C 8 H 17 (DMOA) or n-C 10 H 21 (DMDA) increase dramatically upon going from dilute non-micellar to concentrated micellar solutions, thus shifting the NMR kinetic window towards acidic pHs by ca. 2 units. Experiments performed at constant pH and at variable salt concentrations C reveal a sharp rate increase as C is brought beyond the critical micellar concentration (CMC); such operations can constitute a very sensitive new procedure for CMC determination. Herein, the influence of the pH and of the structure of the ammonium salts is examined in order to elucidate the mechanisms contributing to proton exchange in micelles.As a first step, proton transfers on DMOA were studied at a range of concentrations between 0.01 and 0.25 m, well below the CMC, and at pH 3 to 5 in order to bring exchange rates within the NMR kinetic window (1-30 s À1). 1 H NMR spectra were recorded at 400 MHz with suppression of the water resonance. Exchange rates were obtained from total line shape analysis of the N-methylic pattern (see Figure 1). The deprotonation of BH + into its conjugate base B is the slow and measurable step, followed by an immeasurably fast reprotonation of B, which ends the proton exchange. In the process, the nuclear spin state of the exchanging proton randomly flips between a and b; this is equivalent to observing an NMR site exchange between the two components of the coupled N-methylic doublet with a frequency k NMR (s À1

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