DODECYL TRIMETHYL

Analoge reduktive Demethylierungen lassen sich auch mit Natrium-boranat durchfuh-ren, z. B. N,N,N-Trimethyl-anilinium-jodid in Dimethyl-sulfoxid zu N,N-Dimethyl-anilin (96%) und Dodecyl-trimethyl-ammonium-bromid in Phosphorsaure-tris-[dimethylamid] (HMPT) zu 1-Dimethylamino-dodecan (65%)1. 

CTAB/DTAB = Cetyl/Dodecyl trimethyl ammonium bromide, DSB = Dodecyl sulfo betaine... 

The cationic surfactant is selected on the basis of the amount of conditioning desired, the more hydrophobic cationic such as a dihydrogenated tallow dimethyl ammonium chloride provides a high level of conditioning, while the same molecular architecture based on di-palmityl-dimethyl ammonium chloride provides a lower level of conditioning. Still milder conditioning for oily hair can be provided by mono alkyl chain cationics such as dodecyl-trimethyl ammonium chloride. 

FIGURE 7.11 Structure of a common anionic surfactant, sodium dodecyl sulfate (SDS), and, a cationic surfactant, dodecyl trimethyl ammonium bromide (DTAB) (from Refs. 56,57). 

CMCs of these polyfluorinated surfactants are of the order of 10 5 m.47 Plots of the observed H chemical shifts versus surfactant concentration of cetyl trimethyl ammonium chloride, cetyl pyridinium chloride, cetyl dimethyl phenyl ammonium chloride, cetyl dimethyl benzyl ammonium chloride, cetyl dimethy 1-2-phenyl ethyl ammonium chloride, and cetyl dimethyl-3-phenyl propyl ammonium chloride, are sigmoidal and were fitted to a model based on the mass action. The H chemical shift-based CMC values are in excellent agreement with those determined by the surface tension method.48 The micellization processes of dodecyl trimethyl ammonium halides (chloride and bromide) studied by calorimetric titration show different behaviors at 298 K. However, these disappear at 313 K, while the results measured by the chemical shift versus surfactant concentration do not show this difference.49 The CMC of 3-aminopropyl triethoxy silane in toluene is ca. 0.47m, measured by H and l3C chemical shifts.50 The CMC of optically active potassium A -n-dodecanoyl alaminate measured by H and l3C chemical shifts is lower (11-15 him) in D20 than that in a mixed solvent of 1,4-dioxane and D20 (19mM).-51 The H chemical shift shows that the CMC of resorcinol-type calix[4] phosphoric esters having four alkyl side-chains, [4]Ar 5P-R-n, is insensitive to the length of the side-chains, n.52 The CMC values of a family of surfactants, the sodium cyclohexyl alkanoates, with different lengths of the alkanoate side-chains, were obtained from 13C chemical-shift measurements. The results show that these amphiphiles have high CMCs (0.12-1.02 m).-53... 

Interactions between oppositely charged micelles in aqueous solutions spontaneously form vesicles. The self-diffusion coefficient of water and 2H relaxation of 2H-labeled dodecyl trimethyl ammonium chloride of the dodecyl trimethyl ammonium chloride-sodium dodecyl benzenesulfonate systems show that in these mixtures there is limited growth of the micelles with changes in composition. The vesicles abruptly begin to form at a characteristic mixing ratio of the two surfactants. The transition is continuous.205 Transformation from micelle to vesicle in dodecyl trimethyl ammonium chloride-sodium perfluoro-nonanoate aqueous solution has been studied by self-diffusion coefficient measurements, and it was found that at a concentration of 35 wt% with a molar ratio of 1 1, the self-diffusion coefficient of the mixed micelles is far smaller than that of the two individual micelles.206 The characteristics of mixed surfactant... 

The surfactant concentration that induces sign reversal to positive increases with the number of methyl groups from dodecyl ammonium (3x10 ) to dodecyl trimethyl ammonium (10 mol dm ... 

Alkyl trimethyl ammonium chloride, where R contains 8-18 C atoms, for example dodecyl trimethyl ammonium chloride, CjjHjjlCHjljNCl... 

Figure 2.3 illustrates the results of studies on dodecyl trimethyl ammonium bromide (DTAB) at different additions of NaBr [75]. It is seen that with increasing salt concentration the shape of the curve varies and becomes displaced towards lower surfactant concentrations. The... 

Similar results were also obtained for dodecyl trimethyl ammonium bromide (C12TAB) with different additions of NaBr (cf Fig. 2.3). However, the shape of the surface tension isotherm becomes essentially different when the mean value of the ionic product c is used instead of the surfactant concentration c. The experimental isotherms of C12TAB plotted the mean... 

The Fig. 2.4 of Chapter 2 illustrates the surface tension of dodecyl trimethyl ammonium bromide (C12TAB) at different NaBr concentrations [79] as a function of the mean ionic... 

Fig. 3.70. Mixtures of sodium dodecyl sulphate (Na R ) and dodecyl trimethyl ammonium bromide (R Br ), at constant total concentration of 0.03 mmol/1, experiments according to [89], solid line - theory for adsorption of R R and desorption ofNaBr.

A simple analysis of this equation shows that the slope of the isotherm at usual values of P = 0.5 and vz/v - 0.5 should decrease drastically at the transition to the CMC. Eq. (5.144) was used later by Prokhorov and Rusanov for the evaluation of P from the surface tension of aqueous solutions of dodecyl trimethyl ammonium bromide (DTAB) [63]. The obtained value proved to be too high in comparison with the findings of independent methods. A possible reason of this discrepancy can be the assumptions used for the derivation of Eq. (5.144). Namely, the condition i = 1 can hold only at concentrations essentially exceeding the CMC. A... 

A relatively new field is the use of flotation in wet textile processes [73]. The ( -potential of cotton fibres in aqueous solutions is negative, therefore they are effectively floated by cationics like quaternary ammonium salts, e.g. dodecyl trimethyl ammonium chloride. Sysilia et al. [74] have established, by measuring the electrokinetic potential, a clear rule between the positive surface charge of chromite and flotation efficiency. At low pH, chromite was effectively floated by fatty acid soaps, the ions of which are negatively charged under these conditions. The surfactant adsorption is reversible which is indicative of its physical nature. 

The so-called synthetic fibres, e.g. nylon, show their peculiarities of wetting in the presence of surfactants of various nature. Capillary wetting rates of nylon fibrous assemblies were studied in [172] using conductivity measurements as well as contact angle measurements by the Wilhelmy method. For sodium dodecyl sulphate and dodecyl trimethyl ammonium chloride a minimum wetting rate was observed near pH 4, which coincided with the isoelectric point of the nylon fibre. When the surface charge increased, the wetting rate increased. 

Neutral additives such as hydroxy ethyl cellulose or polyvinyl alcohol increase the viscosity of the run buffer and thus reduce the veof- Furthermore, they suppress analyte-surface interactions. Similarly, organic solvents such as methanol and acetonitrile can be used to reduce or increase the viscosity respectively. Cationic surfactants such as dodecyl trimethyl ammonium bromide (DoTAB) adsorb onto the capillary walls and thus change the surface charge. This reverses the direction of the EOF. Surfactants must be used at low concentrations to avoid the formation of micelles, which may interfere with the separation process (section 3.3). 

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