Cetyl trimethyl ammonium bromid

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Cetyl trimethyl ammonium bromide [CTAB]/w-alkanol [13-15]... 

Note PEO = polyethylene oxide PVA = polyvinyl alcohol SDS = sodium dodecyl sulfate CTAB = cetyl trimethyl ammonium bromide. 

CTAB, cetyl trimethyl ammonium bromide STAC, stearyl trimethyl ammonium chloride DSDMAC, distearyl dimethyl chloride. 

Surface-active agents used as adjuvants in pharmaceutical preparations to improve drug dissolution may affect the stability of /3-lactams. Thus, the presence of micelles of cetyl(trimethyl)ammonium bromide (CTAB) enhanced up to 50-fold the rate of alkaline hydrolysis of penicillins [140]. In the case of cephalosporins, micelle-promoted catalysis of the intramolecular degradation process (see Sect 5.2.2) was also observed [85][141], It has been proposed that the negatively charged penicillins and cephalosporins are attracted by the cationic micelles. This attraction increases substrate concentration in the micellar phase, in turn accelerating the rate of HO- ion attack. Ion exchange at the micellar surface and electrostatic stabilization of the transition state may also contribute to the increased rate [142][143],... 

Dialkyl tellurides (general procedure) A mixture of TUDO (0.2 g, 2 mmol), NaOH (0.112 g, 2.6 mmol), Te powder (0.128 g, 1 mmol) in H2O (0.75 mL) and THF (0.75 ml) is refluxed for 1 h. The alkyl halide (2 mmol) and (cetyl trimethyl ammonium bromide) CTBA (0.004 g, 1.1 X 10 mmol) in THF (0.5 mL) are added to the pale pink solution. After 1 h of additional reflux the mixture is worked up in the usual manner and the residue purified by column chromatography on Si02 (elution with petroleum ether 40-60°C). 

Surfactants such as cetyl trimethyl ammonium bromide (CTAB), Triton X-100 (TX-lOO) and sodium dodecyl sulphate (SDS) are the most commonly used. CTAB forms large micelles [24-26] with aggregation number 61, cmc 9.2 X 10 M, and a positive micellar Stem layer TX-lOO has aggregation number 139 with neutral OH groups on the Stern layer, and SDS forms negative micelles with cmc 8.3 x 10 M and aggregation number 131. The... 

SDS sodium dodecyl sulphate CTAB cetyl trimethyl ammonium bromide TX-lOO Triton X-100 Mb myoglobin... 

Triazine containing polysulfides having high molecular weights have been readily synthesized by the phase-transfer catalyzed polycondensation of 6-diethylamino or dibutylamino-l,3,5-triazine-2,4-dithiols with 1,10-dibromodecane in the presence of cetyl trimethyl ammonium bromide in a nitrobenzene-aqueous alkaline solution system <99MI294>. 

Schultz and Matijevic (16) prepared nanoparticles of palladium sulfide (PdS) by the continuous double-jet mixing of PdCl2 or Na2(PdCl4) and Na2S. They found that the particle size was 20-30 nm in mean diameter obtained in acidic media (pH = 2-3), but 2-5 nm in alkaline media, probably due to the high equilibrium concentration of sulfide ions S2- by dissociation of H2S and HS in the alkaline media (pH = 10-12). A cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), was found to be useful for stabilizing the small particles prepared in alkaline media. 

CTAB surface area m2/g ASTM D 3765 ISO 6810 adsorption of CTAB (cetyl trimethyl ammonium bromide) from aqueous solution as a measure of the specific outer surface area... 

Figure 4.22 ir-A curves for cetyl trimethyl ammonium bromide at air-water and oil-water interfaces at 20°C... 

Baxendale, Evans and coworkers reported in 1946 that the polymerization of methyl methacrylate (MMA) in aqueous solution was characterized by homogeneous solution kinetics, i.e. where mutual termination of free radicals occurred, in spite of the fact that the polymer precipitated as a separate phase. Increases in the rates of polymerization upon the addition of the surfactant cetyl trimethyl ammonium bromide (CTAB) were attributed to the retardation of the rate of coagulation of particles, which was manifested in a reduction in the effective rate constant for mutual termination,... 

Two other shapes of micelles may be considered, namely, the rod-shaped micelle suggested by Debye and Anacker and the lamellar micelle suggested by McBain. The rod-shaped micelle was suggested to account for the light-scattering results of cetyl trimethyl ammonium bromide in KBr solutions, whereas the lamellar micelle was considered to account for the X-ray results in soap solutions. A schematic picture of the three type of micelles is shown in Fig. 2. 

Cetyl trimethyl ammonium bromide O +(CH2CHO)nH O rcn(ch2)2n(ch2)2ncr ch3oso- 1% ... 

A detailed study of the interaction of hydrocarbons with cetyl trimethyl ammonium bromide modified montmorillonite has been done using Raman spectroscopy [82]. The quaternary salt was observed to be in a liquid-like state and it was concluded that interaction of organic compounds in this system is best classified as absorption. 

In this area, recent unrelated efforts of the groups of Bhattacharya and Fife toward the development of new aggregate and polymer-based DAAP catalysts deserve mention. Bhattacharya and Snehalatha [22] report the micellar catalysis in mixtures of cetyl trimethyl ammonium bromide (CTAB) with synthetic anionic, cationic, nonionic, and zwitterionic 4,4 -(dialkylamino)pyridine functional surfactant systems, lb-c and 2a-b. Mixed micelles of these functional surfactants in CTAB effectively catalyze cleavage of various alkanoate and phosphotriester substrates. Interestingly these catalysts also conform to the Michaelis-Menten model often used to characterize the efficiency of natural enzymes. These systems also demonstrate superior catalytic activity as compared to the ones previously developed by Katritzky and co-workers (3 and 4). 

CBH. The sparingly water soluble compound of heparin with an organic base (BH), such as benzalkonium—e.g., Zephiran (Winthrop) or cetyl trimethyl ammonium bromide or octadecyl amine can be dissolved in ethyl alcohol and mixed with an organic polymer matrix—e.g., collodion in ether and alcohol (4). Such lacquer mixtures are designated CBH. 

In view of the experimental model in the above studies by Jain and Wu [16], the effect of SDS on protein domains cannot be surmised however, similar thermal behavior has been reported for human SC following treatment with the surfactants SDS and cetyl trimethyl ammonium bromide, both of which... 

Eliasson and Ljunger (33) reported that the cationic surfactant cetyl trimethyl-ammonium bromide (CTAB) slowed down the rate of formation of amylopectin crystallites in gelatinized waxy maize starch, as measured by differential scanning calorimetry (DSC). 

CTAB Cetyl Trimethyl Ammonium Bromide CisH N(CH3)3Br ... 

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