Phase hexadecyltrimethylammonium bromide

The geometry and surface chemistry of the dendrimer assemblies can be varied through the addition of surfactants. These dendrimer/surfactant aggregates can be tuned to template the formation of the different phases of calcium carbonate [40]. In combination with hexadecyltrimethylammonium bromide (CTAB), small spherical aggregates were formed that induce the formation of vaterite. Over a period of five days, the vaterite was transformed into calcite. The use of the negatively charged surfactant, sodium dodecylsulfonate (SDS), result-... 

Two molecules of carbon monoxide were successively incorporated into an epoxide in the presence of a cobalt catalyst and a phase transfer agent [29]. When styrene oxide was treated with carbon monoxide (0.1 MPa), excess methyl iodide, NaOH (0.50 M), and catalytic amounts of Co2(CO)8 and hexadecyltrimethylammonium bromide in benzene, 3-hydroxy-4-phenyl-2(5H)-furanone was produced in 65% yield (Scheme 7). A possible reaction mechanism was proposed as shown in Scheme 8 Addition of an in situ... 

A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na, and acesulfame-K), preservatives (sodium dehydroacetate, SA, salicyclic acid, BA, succinic acid, methyl-para-hydroxybenzoic acid, ethyl-para-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 ml aqueous tr-hydroxyisobutyric acid solution (pH 4.5) (2.2 3.4 or 2.4 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a Clg column with a flow rate of 1.0 ml/min and detection at 233 nm were used. This method was found to be very reproducible detection limits ranged from 0.15 to 3.00 p,g. The retention factor (k) of each additive could be affected by the concentrations of hexadecyltrimethylammonium bromide and a-hydroxyisobu-tyric acid and the pH and ratio of mobile phase. The presence of additives in dried roast beef and sugared fruit was determined. The method is suitable for routine analysis of additives in food samples (81). 

Fig. 2.20. Phase diagram (at 25 °C) from the work by Ekwall and co-workers (cf. Refs.8 86)) for the three-component system hexadecyltrimethylammonium bromide (CTAB) - hexanol -water. Li denotes a region with water-rich solutions L2 a region with hexanol-rich solutions D and E are lamellar and hexagonal liquid crystalline phases, respectively. In the figure are also schematically indicated the structures of normal (Lj region) and reversed (L2) micelles as well as of the liquid crystalline phases. (From Ref.9Sb...

DNA from those sources rich in polysaccharides can be purified by the addition of CTAB (hexadecyltrimethylammonium bromide) before chloroform isoamyl alcohol extraction [6], After adjusting NaCl concentration to 0.7 M with 5 M NaCl in a DNA solution solution (ca. 0.05 mg/mL in TE), CTAB solution (10% CTAB in 0.7 M NaCl) is added so that the final concentration of CTAB is about 1%. The samples are incubated at 65°C for 10 minutes. It is important to keep the salt at a concentration of greater than 0.5 M so that the DNA does not precipitate as a CTAB-DNA complex. After the addition of an equal volume of chloroform-isoamyl alcohol (24 1 by volume) and gentle but complete mixing, the phases are separated by centrifugation for 10 minutes at 2000 x g. The interphase will appear as a white precipitate of CTAB-polysaccharides/protein complex. The aqueous phase containing DNA is transferred with a wide-bore pipette to a tube, and the CTAB chloroform-isoamyl alcohol extraction can be repeated until no cellular material is visible at the interphase. The DNA from the aqueous phase is precipitated with ethanol as described earlier, and any residual CTAB is washed with 70% ethanol washes. 

A high performance liquid chromatographic procedure has been described [3] for the simultaneous determination of the fungicides sodium-A-methyldithiocarbamatc and methylisothiocyanate in surface waters and in sewage, based on their separation on a reversed phase column with a miscellar mobile phase (hexadecyltrimethylammonium bromide) in 1 1 v/v methanohwater buffered to pH6.8. Detection Limits were 70 and lpg dm 1 when the analysis was performed with an ultraviolet detector at 247nm. 

The parameters P(l) and P(2) define the solubilization stage. In the absence of micelles, there is no solubilization of the oil phase. Therefore, in this case, there are no values of P(l) and P(2), e.g., as for the 1 6 hexadecyltrimethylammonium bromide-cetyl alcohol molar ratio. 

Most of the work concerned with micellar catalysis of nucleophilic substitution refers to reactions of the Aac2 and SN2 types and will not be reviewed here. To date only a few systems have been examined in which a micellar medium affects the partitioning of solvolytic reactions between unimolecular and bimolecular mechanisms. The effects of cationic (hexadecyltrimethylammonium bromide = CTAB) and anionic (sodium lauryl sulfate = NaLS) micelles on competitive SN1 and SN2 reactions of a-phenylallyl butanoate 193) have been investigated189. The rate of formation of the phenylallyl cation 194) is retarded by both surfactants probably as a consequence of the decreased polarity of the micellar pseudo phase. The bimolec-... 

Mobile phase 10 mM pH 7.0 phosphate buffer containing 0.55 mM hexadecyltrimethylam-monium bromide (Condition column before use with 0.5% hexadecyltrimethylammonium bromide.)... 

Mobile phase MeCN pH 7.0 Titrisol phosphate buffer (Merck) water 500 50 450, containing 4 gTL hexadecyltrimethylammonium bromide Flow rate 1.5 Ipjection volume 60 Detector UV 274... 

Mobile phase MeOH 40 mM potassium phosphate -I- 20 mM sodium phosphate 65 35, containing 2 g/L hexadecyltrimethylammonium bromide, pH acijusted to 7.4 with HCl Flow rate 1... 

An aqueous mixture of benzene, hydrogen peroxide, ferric nitrate and a catalytic proportion of hexadecyltrimethylammonium bromide at 35-50 C has been claimed to afford an 82% yield of phenol although this was only 8-10% without the phase-transfer catalyst (ref. 13). 

CE CGE CHOL CIP CPG CTAB CZE dA, dG, dC DBU DEAE DMF DMT DNP DOPE DOTMA EDTA EM EOF ESI-MS Fmoc FPE ICAM-1 Capillary electrophoresis Capillary gel electrophoresis Cholesterol Cahn-Ingold-Prelog nomenclature system for absolute configuration Controlled pore glass Hexadecyltrimethylammonium bromide Capillary zone electrophoresis Deoxyadenosine, deoxyguanosine, deoxycytosine l,8-Diazabicyc o[5.4.0]undec-7-en Diethylaminoethyl- Dimethylformamide Bis(4-methoxyphenyl)phenylmethyl-, (syn. Dimethoxytrityl-) 2,4-DinitrophenyI- Dioleylphosphatidylethanolamine N-[l-(2,3-dioleyloxy)propyl]-N, N, N-trimethylammonium chloride Ethylenediamine tetra-acetic acid Electrophoretic mobility Electro-osmotic flow Electrospray ionization mass spectrometry 9-Fluorenylmethoxycarbonyl-Fluid phase endocytosis Intracellular Adhesion Molecule-1... 

Baldwin and Widdison prepared ethyl a-deuterodiazoacetate by reacting ethyl-diazoacetate with two different batches of sodium deuteroxide in deuterium oxide containing hexadecyltrimethylammonium bromide as a phase transfer catalyst. A proton NMR analysis showed the product was more than 98% deuterated at the a-carbon. The deuter-ated diazoacetate was then converted into two diastereomeric ethyl-(2-bromo-2-methylcyclopropane-1 -d) carboxylates by reaction with 2-bromopropene and a rhodium(II)... 

Cava and co-workers have extended this reaction to sulfoxides using 30% aqueous sodium hydroxide at 80-100°, usually in the presence of a phase-transfer catalyst (hexadecyltrimethylammonium bromide). 

Chromium trioxide I hexadecyltrimethylammonium bromide Oxo compds. from alcohols 2-Phase medium s. 44, 233... 

Aq. NaOCl added to a stirred soln. of benzyl alcohol in 0.02 M aq. Na-stearate at room temp., and stirring continued overnight benzaldehyde. Y 90%. The method is very cheap and work-up uncomplicated however, reaction appears limited to arylcarbinols and sec. alcohols in the absence of micelles little or no reaction was observed. F.e., also oxidation with hexadecyltrimethylammonium chromate, or preferably in a 2-phase medium with CrOj/hexadecyltrimethylammonium bromide, s. B. Jursic, Synthesis 1988, 868-71. 

A partition of the transparent isotropic water-in-oil type solubilization area has been proposed as well by Smith and others (20,21) who investigated the phase and structural behavior of oil-continuous systems composed of water, hexane, 2-propanol, with or without addition of hexadecyltrimethylammonium bromide or perchlorate. The techniques used were conductometry, ultracentrifugation and, later, NMR. Smith and coworkers (20) put into evidence kinks on conductivity curves as the system composition was varied by increasing 2-propanol content. Plotting in the phase diagram... 

The synthesis of 4,4 -dibromobenzilic acid via the benzilic acid rearrangement of 4,4 -dibromobenzil (22) proceeded rapidly with high yields." The use of KOH in benzene and methanol in the presence of hexadecyltrimethylammonium bromide as a phase-transfer catalyst afforded 96% yield of the pure acid 23 in 3 h at room temperature. 

There is little effect of micelles upon the rate of an intramolecular nucleophilic reaction. Micelles of hexadecyltrimethylammonium bromide catalyse, by factors of 10 —10, the arenesulphinate anion-induced hydrolysis of 4-tolylsulphonyl-methyl perchlorate. There is no relationship between the rate acceleration and hydro-phobicity of the sulphinate anion and catalysis is attributed to the concentration of the reactants in the micellar phase.The rate constants for the reaction of nucleophiles with carbonium ions and those for the addition of cyanide ion to the A -alkylpyridinium ions are similar in the micellar and aqueous phases, and the rate enhancement is due to the concentration of reactants in the micellar pseudophase. Similarly, although micellar catalysed dephosphorylation by nucleophiles may show rate enhancements of up to 4 x 10 -fold, the second-order rate constants may be slightly smaller in the micellar pseudophase lowing to its lower polarity. However, the reaction of fluoride ion with 4-nitrophenyldiphenyl phosphate is very rapid in micelles of cetyltrimethylammonium fluoride, but the rate constant continues to increase when the substrate is fully bound with increasing cetyltrimethylammonium fluoride or sodium fluoride. The failure of the micellar pseudophase model is also apparent in the reaction of hydroxide ion with 2,4-dinitrochlorobenzene. It is suggested that reaction occurs between reactants in the aqueous and micellar pseudophases and also between hydroxide ion in water and substrate in the micelle. ... 

As there is a lack of detailed phase diagrams exhibiting lyotropic phase chirality it may be sufficient to discuss briefly the polymorphism of two frequently used achiral systems. The first example is presented by the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) in a binary mix-... 

Figure 14.6. Phase diagrams of lyotropic mixtures (temperature versus amphiphile concentration), (a) Hexadecyltrimethylammonium bromide (CTAB)/water, after [50]. L isotropic micellar solution hexagonal phase V bicontinuous cubic phase L lamellar phase C several heterophasic regions containing crystalline components Nc nematic phase of rod-like micelles, (b) Cesium pentadecafluorooctanoate (CsPFO)/water, after [8].

Andres, M. P. S., J. Otero, and S. Vera. 2011. High performance liquid chromatography method for the simultaneous determination of a-, P-, and y-tocopherol in vegetable oils in presence of hexadecyltrimethylammonium bromide/w-propanol in mobile phase. Food Chem. 126 1470-1474. 

Figure 6.42 Diagrams showing temperatures and surfactant concentration (Cs) at which (a) tartrazine and (b) amaranth-alkyltrimethylammonium bromide solutions separate into two or more phases. Dye concentration 15 mmol 1" hexadecyltrimethylammonium bromide system A tetradecyltrimethylammonium bromide cetrimide O dodecyltri-methylammonium bromide. From Barry and Gray [277] with permission.

---