Sodium dodecyl sulfate kinetics

The kinetics of vinyl acetate emulsion polymeriza tion in the presence of alkyl phenyl ethoxylate surfactants of various chain lengths indicate that part of the emulsion polymerization occurs in the aqueous phase and part in the particles (115). A study of the emulsion polymerization of vinyl acetate in the presence of sodium lauryl sulfate reveals that a water-soluble poly(vinyl acetate)—sodium dodecyl sulfate polyelectrolyte complex forms, and that latex stabihty, polymer hydrolysis, and molecular weight are controlled by this phenomenon (116). 

Sodium dodecyl sulfate and hydrogen dodecyl sulfate have been used as catalysts in the denitrosation iV-nitroso-iV-methyl-p-toluenesulfonamide [138]. The kinetics of condensation of benzidine and p-anisidine with p-dimethylamino-benzaldehyde was studied by spectrophotometry in the presence of micelles of sodium dodecyl sulfate, with the result that the surfactant increases the rate of reaction [188]. The kinetics of reversible complexation of Ni(II) and Fe(III) with oxalatopentaaminecobalt(III) has been investigated in aqueous micellar medium of sodium dodecyl sulfate. The reaction occurs exclusively on the micellar surface [189]. Vitamin E reacts rapidly with the peroxidized linoleic acid present in linoleic acid in micellar sodium dodecyl sulfate solutions, whereas no significant reaction occurs in ethanol solution [190]. 

Mechanisms of micellar reactions have been studied by a kinetic study of the state of the proton at the surface of dodecyl sulfate micelles [191]. Surface diffusion constants of Ni(II) on a sodium dodecyl sulfate micelle were studied by electron spin resonance (ESR). The lateral diffusion constant of Ni(II) was found to be three orders of magnitude less than that in ordinary aqueous solutions [192]. Migration and self-diffusion coefficients of divalent counterions in micellar solutions containing monovalent counterions were studied for solutions of Be2+ in lithium dodecyl sulfate and for solutions of Ca2+ in sodium dodecyl sulfate [193]. The structural disposition of the porphyrin complex and the conformation of the surfactant molecules inside the micellar cavity was studied by NMR on aqueous sodium dodecyl sulfate micelles [194]. 

The catalytic activities of Cu(II), Co(II) and Mn(II) are considerably enhanced by sodium dodecyl sulfate (SDS) in the autoxidation of H2DTBC (51). The maximum catalytic activity was found in the CMC region. It was assumed that the micelles incorporate the catalysts and the short metal-metal distances increase the activity in accordance with the kinetic model discussed above. The concentration of the micelles increases at higher SDS concentrations. Thus, the concentrations of the catalyst and the substrate decrease in the micellar region and, as a consequence, the catalytic reaction becomes slower again. 

Wilkins. S.J., Coles, B.A., Compton, R.G., and Cowley, A. Mechanism and kinetics of salicylic acid dissolution in aqueous solutionunder defined hydrod3mamic conditions via atortric force trricrosopy the effects of the ionic additives NaCl, LiCl, and MgCb, the organic additives 1-propanol, 2-propanol, and the surfactant sodium dodecyl sulfate. J. Rhys. Chem. B, 1061(106) 4763-4774, 2002. 

A combined effect of natural organic matter and surfactants on the apparent solubility of polycyclic aromatic hydrocarbons (PAHs) is reported in the paper of Cho et al. (2002). Kinetic studies were conducted to compare solubilization of hydro-phobic contaminants such as naphthalene, phenanthrene, and pyrene into distilled water and aqueous solutions containing natural organic matter (NOM) and sodium dodecyl sulfate (SDS) surfactant. The results obtained after 72hr equilibration are reproduced in Fig. 8.19. The apparent solubility of the three contaminants was higher in SDS and NOM solutions than the solubility of these compounds in distilled water. When a combined SDS-NOM aqueous solution was used, the apparent solubility of naphthalene, phenanthrene, and pyrene was lower than in the NOM-aqueous solution. 

Bunton and Robinsont studied the effect of sodium dodecyl sulfate micelles on the rate of the reaction between OH" and 2,4-dinitrochlorobenzene. These negative micelles have an inhibiting effect on the reaction, yet the kinetic data can be analyzed according to Equation (24). Use the following data and the authors CMC value of 0.0064 M to estimate K/n, where K is the binding constant between the dodecyl sulfate micelles and the 2,4-nitrochlorobenzene ... 

Chromic acid oxidation of D-sorbitol and D-mannitol has been studied in the presence and absence of 2,2/-bipyridyl (bipy). A monomeric species of Cr(VI) has been found to be kinetically active in absence of bipy, whereas in the catalysed path the Cr(VI)-bipy complex has been found to be the active oxidant. Sodium dodecyl sulfate... 

Espin, J. C., and Wichers, H. J. (1999). Activation of a latent mushroom (Agaricus bisporus) tyrosinase isoform by sodium dodecyl sulfate (SDS). Kinetics properties of the SDS-activated isoform. J. Agric. Food Chem., 47, 3518-3525. 

Abstract Investigations of alternate adsorption regularities of cationic polyelectrolytes a) copolymer of styrene and dimethylaminopropyl-maleimide (CSDAPM) and b) poly(diallyldimethylammonium chloride) (PDADMAC) and anionic surfactant - sodium dodecyl sulfate (SDS) on fused quartz surface were carried out by capillary electrokinetic method. The adsorption/desorption kinetics, structure and properties of adsorbed layers for both polyelectrolytes and also for the second adsorbed layer were studied in dependence on different conditions molecular weight of polyelectrolyte, surfactant and polyelectrolyte concentration, the solution flow rate through the capillary during the adsorption, adsorbed layer formation... 

Consequently, new investigations dealing with reactions in micellar solutions composed of functional surfactants, or mixtures of inert and functional surfactants, continue to appear in the literature. An interesting study of acid-catalyzed hydrolysis of 2-(p-tetradecyloxyphenyl)-l,3-dioxolane (p-TPD) in aqueous sodium dodecyl sulfate (SDS) solutions has been reported [13]. In this case,/ -TPD behaves as a non-ionic functional surfactant and apparently forms non-ideal mixed micelles with the anionic surfactant (SDS). Based on the observed kinetic data, the authors propose that, at elevated temperatures, the thermodynamic non-ideality results in the manifestation of two populations of micelles, one rich in SDS and the other rich in/>-TPD. 

Several studies since then have supported this suggestion, and now it is widely accepted that conformational change/structural perturbation is a prerequisite for amyloid formation. Structural perturbation involves destabilization of the native state, thus forming nonnative states or partially unfolded intermediates (kinetic or thermodynamic intermediates), which are prone to aggregation. Mild to harsh conditions such as low pH, exposure to elevated temperatures, exposure to hydrophobic surfaces and partial denaturation using urea and guanidinium chloride are used to achieve nonnative states. Stabilizers of intermediate states such as trimethylamine N-oxide (TMAO) are also used for amyloidogenesis. However, natively unfolded proteins, such as a-synuclein, tau protein and yeast prion, require some structural stabilization for the formation of partially folded intermediates that are competent for fibril formation. Conditions for partial structural consolidation include low pH, presence of sodium dodecyl sulfate (SDS), temperature or chemical chaperones. 

The properties of formulations F31 and F were measured in ENSLIN equipment in order to compare the kinetics of water uptake and to study the dissolution profile, as shown in Figures 16-19. As observed in Figure 19, the dissolution of plant extract after 60 min is very slow when pH-modified (NA2C03) and sodium dodecyl sulfate (SDS) are not used (almost not change in color for formulation F). 

Aqueous emulsions of styrene, methyl methacrylate, methyl acrylate, and ethyl acrylate were polymerized with y-radiation from a Co source in the presence of sodium dodecyl sulfate or sodium laurate. The continuous measurement of conversion and reaction rate was carried out dilato-metrically. The acrylates polymerized fastest and the over-all polymerization rate increased as follows styrene < methyl methacrylate < ethyl acrylate methyl acrylate. The effects of radiation dose, temperature, and original monomer and emulsifier concentrations were studied with respect to the following factors properties of polymer dispersions, number and size of polymer particles, viscometrically determined molecular weights, monomer-water ratio, and kinetic constants. 

We have speculated on but do not understand the mechanism causing the lytic activity of laetisaric acid. The active twelve carbon metabolite of laetisaric acid may poison a key enzyme in lipid metabolism or disrupt the integrity of the fungal cell membrane by insertion or dissolution as has been shown in Escherichia coli with sodium dodecyl sulfate and Triton X-100 (24 r 25). Why the C-12 molecule is most active remains to be determined. Kinetic studies of lipid metabolism and physicochemical and ultrastructural investigations of membranes treated with the putative active metabolite may answer these questions. 

Actinomycin D dissociation kinetics were measured on a Cary 219 spectrophotometer equipped with a magnetic stirrer and thermostated cell holders. Sodium dodecyl sulfate (SDS) was used to sequester dissociating actinomycin D, and the resulting Increase In absorbance was monitored at 452 nm as a function of time. Stop-flow studies (daunorubicin and daunorubicin/ actinomycin D) were conducted with a Durrum-Glbson Model 110 stopped-flow spectrophotometer equipped with a dual detector accessory and a Tektronix storage oscilloscope Interfaced with a PDF 11/34 computer. Experiments were done In a 0.01M Na phosphate buffer, 0.1M NaCl, 0.001M NaEDTA, pH=7. Dissociation time constants were computed with a multlexponentlal analysis computer program. 

The enhancement of reaction rate as well as the stereoselectivity of hydrolytic reactions were studied by several authors [47]. Typical substrates were hydro-phobized activated esters of amino acids and typical catalysts were surface active peptides with histidine as active component. The kinetic resolution of racemic esters was determined. Brown [48] and Moss [49] gave explanations for the stereoselectivity. Ueoka et al. [50] reported one example where non-function-al amphiphiles as cosuxfactants can enormously improve the stereoselectivity the saponification of D,L-p-nitrophenyl J -dodecanoylphenylalaninate with the tripeptide Z-PheHisLeu-OH as catalyst in assemblies of ditetradecyldimethylam-monium bromide yielded practically pure L-M-dodecanoylphenylalanine upon the addition of between 7 to 20 mol % of the anionic surfactant sodium dodecyl sulfate (SDS). 

Figure 34. Determination of micellar charge from equilibrium and kinetic measurements. The decrement of micellar charge as a function of sodium dodecyl sulfate added to Brij 58 micelles was calculated from the pK shift according to Gouy-Chapman equation (/ = lOm/W) (A) or from the second-order rate constant of protonation using Debye s equation (Eigen etal., 1964) for rates measured in the presence of ionic screening (O) at/ = 10mM,or from rates extrapolated to / = 0 ( ) (Gutman et al., 1981a).

Micellar media are formed from tensioactive molecules in aqueous solution. Mi-cellization is a manifestation of the strong self-association of water and water-like solvents [95]. Micelles are known to increase the solubilization of weakly polar substances in water and, as a consequence, their presence determines the magnitude of hydrophobic interactions. Micelles aggregate spontaneously in aqueous solution beyond a critical concentration which is a function of pressure [96]. As a result, pressure may induce an extra kinetic effect on the rate of organic reactions carried out in aqueous micellar systems. Representative ionic micelles are sodium dodecyl sulfate (SDS) and tetradecyltrimethylammonium bromide (TTAB). Recent examples demonstrate the beneficial effect of the presence of surfactants in Lewis acid-catalyzed reactions, a kind of biactivation [97]. 

It must be noted that the dynamic nature of micelles must especially be borne in mind in dealing with electron transfers which invariably are fast processes. The seminal work of Bruhn and Holzwarth [88], an examination of the kinetics of diffusion-controlled electron transfer reactions in micellar sodium dodecyl sulfate solutions, disclosed that sufficient heed must be paid to the continuous disintegration and reconstitution of the micelles in this time range. 

The kinetics of the electron transfer reactions between Ce(IV) and a series of substituted alkoxycarbonylbipyridine complexes (table 9) were determined in homogeneous solutions and in the presence of varying concentrations of sodium dodecyl-sulfate (SDS) (Vincenti et al. 1985b). The results show a complex dependence of the rates of the electron transfer reaction on the concentration of the micelle. There is a surprising increase in rate at concentrations below the critical micelle concentration, which the authors attribute to the formation of Fe(II)-SDS complexes. 

---