Sodium dodecylsulfate, micelle water

Gesell, J., Zasloff, M. and Opella, S.J. (1997) Two-dimensional 1H NMR experiments show that the 23-residue magainin antibiotic peptide is an alpha-helix in dodecylphosphocholine micelles, sodium dodecylsulfate micelles, and trifluo-roethanol/water solution. J. Biomol. NMR 9, 127-135. 

Abraham, M.H., Chadha, H.S., Dixon, J.P., Rafols, C. and Treiner, C. (1995a) Hydrogen bonding. Part 40. Factors that influence the distribution of solutes between water and sodium dodecylsulfate micelles. J. Chem. Soc. Perkin Trans. 2, 887-894. 

Subsequently, cationic rhodium catalysts are also found to be effective for the regio- and stereoselective hydrosilation of alkynes in aqueous media. Recently, Oshima et al. reported a rhodium-catalyzed hydrosilylation of alkynes in an aqueous micellar system. A combination of [RhCl(nbd)]2 and bis-(diphenylphosphi no)propanc (dppp) were shown to be effective for the ( >selective hydrosilation in the presence of sodium dodecylsulfate (SDS), an anionic surfactant, in water.86 An anionic surfactant is essential for this ( )-selective hydrosilation, possibly because anionic micelles are helpful for the formation of a cationic rhodium species via dissociation of the Rh-Cl bond. For example, Triton X-100, a neutral surfactant, gave nonstereoselective hydrosilation whereas methyltrioctylammonium chloride, a cationic surfactant, resulted in none of the hydrosilation products. It was also found that the selectivity can be switched from E to Z in the presence of sodium iodide (Eq. 4.47). 

Other surfactants, such as cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS), and polyethoxylates (Iegpal, Brij, and Tween), have also been used. In addition to these stmctural differences, experiments measuring the dynamics revealed that the motion of the water molecules inside the micelle differs from that in the bulk. 

Relatively small retardations of the rate of the base catalyzed hydrolysis of methyl-1-naphthoate by sodium dodecylsulfate (NaLS) and hexadecyltrimethylammonium bromide (CTAB) in 50 wt percent dioxane-water have been observed. These effects were attributed to micelle formation in this solvent system since plots of In where 2 and are the second order rate constants in the presence and absence of the organic salts, vs. the concentration of the salts were non-linear... 

Detergent molecules can stabilize the emulsion of oil in water as well as remove dirt from soiled clothes. A typical detergent is sodium dodecylsulfate (SDS), which has a formula of CH3(CH2)i0CH2SO4 Na+. In aqueous solution, SDS suspends oil or dirt by forming small aggregates of detergent anions called micelles. Propose a structure for micelles. 

Fig. 11. Two-dimensional DOSY spectrum of a sample containing 1,3,5-triisopropylben-zene (TIPB) and mixed micelles in D2O. SDS = sodium dodecylsulfate HOD = partially deuterated water. [Reproduced by permission from Morris and Johnson, 1993.]...

In the case of surfactants it has been observed that sodium dodecylsulfate (SDS), Tergitol 7 [sodium 4-ethyl-1(3-ethylpentyl)octyl sulfate], and CTAB [hexadecyl(trimethyl)ammonium bromide] increase the solubility of Ss in water dramatically, provided the critical concentration for micelle formation is exceeded. For instance, 50 g 1 SDS enhance the solubility of Ss at 20 °C from 5 ng to 20 mg 1 i.e., by a factor of 4000. This enhanced solubility increases further with increasing temperature. It is believed that the surfactant molecules form micelles and that the Ss molecules dissolve in the hydro-phobic interior of these micelles in a similar fashion as in a liquid hydrocarbon solvent [16]. 

The simplest, and at the same time the most effective way to achieve dispersion in water or aqueous media is the addition of amphiphihc molecules carbon nanotubes without any functional groups are hydrophobic. This characteristic may be employed to enclose them in micelles. The surfactant molecules arrange around the single tubes with their hydrophilic head directed outward and their hydrophobic tail oriented toward the nanotube in the center. In this manner, each individual tube is surrounded by an envelop that enables a dispersion, for example, in water. Yet complete solubilization requires considerable amounts of the surfactant. Solutions obtained this way may in fact contain up to 80% of detergent and only 20% of carbon nanotubes. Surfactants suitable to enclose nanotubes in micelles include, for example, sodium dodecylsulfate (SDS), Triton X-100, or octadecyl-trimethylammonium bromide (OTAB). 

The investigation of the kinetics of the solvolysis of p-nitrophenyl bis(chloromethyl) phosphinate 12 in the direct micelles of sodium dodecylsulfate (SDS) in ethylene glycol have demonstrated that the ratio of the factors Fc and Fn, in this system differ from that in aqueous micelles, namely, the positive predominant contribution of the factor of microenvironment to the micellar rate effect is observed (Table 15.1). In the solution of ethylene glycol the micellization is much less effective as compared to the aqueous solution (cmc of SDS in ethylene glycol is equal to 0.18M, while in water it is 0.0085 M) and the micelles formed have low aggregation numbers, a loose structure and a weak solubilization capacity (the binding constants of substrates are lower by two orders of magnitude as compared to those in aqueous micellar solutions). ... 

---