Solubilization of 1,2-ethanediol, ED, and its aqueous solution, ED-W, by the reverse aggregates of sodium bis(2-ethylhexyl) sulfosuccinate, Aerosol-OT or AOT, in n-heptane and isooctane has been studied by FTIR and 1H NMR. Curve fitting of the νOD bands of the aggregate-solubilized (partially deuterated) ED and ED-W showed the presence of a main peak and a smaller one. The frequency of the former peak decreases, whereas its full width at half-height increases as a function of increasing [solubilizate]/[AOT]. The dependence on the later ratio of 1H NMR chemical shifts, δproton, of solubilized water, ED, ED-W as well as the surfactant discrete protons showed monotonic increase or decrease. Results of both techniques indicated that ED and/or water interact with the surfactant by a similar mechanism, i.e., by solvating its head-ions. The magnitudes of |ΔνOD| and |Δδproton| showed, however, that AOT interacts more strongly with ED than with water. Over the entire range of [solubilizate]/[surfactant], the main νOD peak area corresponds to 85 ± 2% (ED), and 88 ± 2% (ED-W) of the total peak area. These results show that the aggregate-solubilized ED or ED-W does not seem to coexist in “layers” of different structures, as suggested by the multi-state water solubilization model.

The solvatochromic behavior of 2,6‐dichloro‐4‐(2,4,6‐triphenyl‐1‐pyridinio)phenolate (WB) was studied by UV–visible spectrophotometry in 32 pure solvents, in binary mixtures of 1‐butanol–cyclohexane (BuOH–Cyhx), and of water with methanol, ethanol, 1‐propanol, 2‐butoxyethanol (2‐BE), acetonitrile, 1,4‐dioxane and THF. The solvent polarity, ET(33) in kcal mol−1, was calculated from the position of the longest‐wavelength intramolecular charge‐transfer absorption band of WB and the results were compared with those for 2,6‐diphenyl‐4‐(2,4,6‐triphenyl‐1‐pyridinio)phenolate [RB, ET(30)] and of 1‐methyl‐8‐oxyquinolinium betaine [QB, ET(QB)]. For pure solvents, ET(33) is a linear function of ET(30), with a slope of practically unity. Steric crowding from the two ortho phenyl rings of RB hinders the formation of H‐bonds with solvents, which results in similar susceptibilities of WB and RB to solvent acidity. For binary solvent mixtures, all plots of ET versus the mole fraction of 1‐butanol or water are non‐linear owing to preferential solvation of the probe by one component of the mixed solvent and, when applicable, to solvent micro‐heterogeneity. Preferential solvation due to non‐specific and specific probe–solvent interactions was calculated for BuOH–Cyhx and water–acetonitrile. Both solvation mechanisms contribute to the non‐ideal behavior in the former binary mixture, whereas probe–solvent specific interactions dominate the solvatochromic behavior in the latter. The composition of the probe solvation shell was calculated. In aqueous alcohols, preferential solvation is by the alcohol. In water–aprotic solvent mixtures, preferential solvation of RB and WB is by the solvent which is present in lower concentration, whereas QB seems to form its own, water‐rich solvation shell over a wide range of water concentration. Copyright © 2000 John Wiley & Sons, Ltd.

The following solvatochromic probes were synthesized: 1-methyl-8-oxyquinolinium betaine (QB), sodium 1 -meth-yWoxyquinolinium betaine-5-sulphonate (QBS), and 1-methyl-3-oxypyridinium betaine (PB). Their solvatochromic behavior in 28 protic and aprotic solvents was investigated, and the data compared to those of 2,6-diphenyl-4-(2,4,6-triphenyl-l-pyridinio)-l-phenolate, (RB). Solvent polarity scales based on QB, QBS, and PB correlate linearly with the ET(30) scale of RB. The Taft-Kamlet-Abboud equation satisfactorily applies to the solvatochromic data of RB, QB, QBS and PB. The multiparameter regression coefficients (a) and (s) of the above mentioned equation show that the sensitivity of the probe to solvent dipolarity/polarizability, and hydrogen bond donation is clearly dependent on its molecular structure. This dependence was tested for a total of 26 probes of widely different structures. It is shown that this is a general behavior, i.e., log Iu I and 1s I are linearly dependent on the pK, and the dipole moment of the probe, respectively.

Solubilization of 1,2,3-propanetriol, PT, and its aqueous solution, PT-W, (W ) water), by reverse aggregates of sodium bis(2-ethylhexyl) sulfosuccinate, Aerosol-OT or AOT, in isooctane has been studied by FTIR and 1 H NMR spectroscopy, and the results were compared with those of solubilization of 1,2ethanediol, ED, and W by the same surfactant. Curve fitting of the IR νOD band of aggregate-solubilized PT or PT-W showed the presence of a main peak and a smaller one. Dependence on [solubilizate]/[AOT] of 1 H NMR chemical shifts, δproton, of solubilized PT, PT-W, as well as the surfactant protons showed monotonic increase or decrease. Both spectroscopic techniques indicated the following order of interaction with AOT: PT > ED > W. Over the entire range of [solubilizate]/[AOT], the main νOD peak areas correspond to 88 ( 2%, and 90 ( 2% of the total peak areas for PT, and PT-W, respectively. This result shows that aggregate-solubilized PT or PT-W do not seem to coexist in "layers" of different structures, as suggested by the multistate solubilization model.