Hexadecyl-trimethylammonium bromide

H. Chaimovich, V. R. Correia, P. S. Araujo, M. V. Aleixo, I. M. Cuccovia, A Quantitative Analysis of the Effect of Hexadecyl-Trimethylammonium Bromide Micelles on the Rate of Alkaline Hydrolysis of Benzylpenicillin , J. Chem. Soc., Perkin Trans. 2 1985, 925-928. 

A preliminary report (10) and a more detailed one (7) of the techniques employed are published elsewhere. Four cationic soaps are used as follows dodecyltrimethylammonium bromide (Ci2TABr,I) hexadecyl-trimethylammonium bromide H (Ci6TABr,II), hexadecylpyridinium chloride (Ci6PyCl,III), and hexadecyldimethylethylolammonium bromide (CioCholBr,IV). The last compound is related to choline bromide,... 

Irradiation of the inclusion crystals of 2a (— )-4 suspended in H20 (containing hexadecyl trimethylammonium bromide) with stirring for 30 h gave a crude reaction product, photocyclization products (+ )-3a, as crystalline materials. This was... 

Then, two MCM-41 materials modified by octyl-dimethyl chlorosilanes were tested. The parent MCM-41 matrices were synthesized by conventional route using hexadecyl-trimethylammonium bromide (sample MTS2) and octadecyl-trimethylammonium bromide (sample MTSl). They exhibit typical peaks of hexagonal ordered mesoporous materials in X-ray diffraction patterns. 

BROMIDE (l-HEXADECYL)TRIMETHYLAMMONIUM BROMIDE LISSOLAMINE MICOL POLL. CID QUAMONIUM SUTICIDE TRIMETHYLCETYL-MIMONIUM BROMIDE N,N,N-TRIMETHYL-1-HEXADECANAMINIUM BROMIDE TRIMETHYL-HEXADECYLAMMONIUM BROMIDE... 

Surface active molecules (surfactants) invariably contain two parts one (hydrophilic) part that prefers to be surrounded by water (the positive charged head of molecule A), and another (hydrophobic) part that prefers to be surrounded by air (or any nonpolar liquid immiscible with water) and shown as a wavy line, called tail. This constitution of the molecule makes it surface active because, clearly, it prefers to be situated at the interface. An example is hexadecyl trimethylammonium bromide (HDTAB) see Fig. 2.2. Not all the soap molecules are adsorbed at the film surfaces a few are present in the core of the film, this number being smaller, the larger the surface activity of the molecule is. The surface activity increases with the length of the tail. The adsorbed soap molecules form a monolayer behaving as a kind of two-dimensional fluid with a certain surface pressure. The (positive) surface pressure is equal to the surface tension of the solution without surfactant minus the surface tension of the solution with surfactant. Between the two surfaces one has the aqueous core containing ions from the added electrolyte (here, K, Br ) and from the soap. 

Fig. 2.2. Chemical formula of a hexadecyl trimethylammonium bromide (HDTAB) molecule.

Films were drawn from solutions containing 8.2x10 mol/dm of purified hexadecyl trimethylammonium bromide (HDTAB) and 8.4 wt% glycerol (added to gain better control of the water vapor pressure equilibrium) in twice-destilled water. The refractive index of the solution was taken (/j= 1.337) the surface tension was y = 39 mN/m (=39 dynes/cm), and the dielectric constant e was 76.2. All measurements were carried out at 25° C. To avoid irregular drainage of the film upon refreshment of the surface inside the vessel, the temperature of the stock solution (see Section VII.B.l) was carefully controlled. 

The viologen reduction by EDTA in reverse micelles in the presence of Ru(bpy)3 is another example of vectorial photoinduced electron transfer [106], The accumulation of photoproducts is associated with the catalytic cycles depicted in Fig. 10(b). The oxidative quenching of the ruthenium complex occurs at the micelle outer boundary, while the regeneration of the dye takes place by the oxidation of EDTA in the inner core of the micelle. The reduction of the final product 4-dimethylaminoazobenzene is further mediated by the acceptor 1-benzylnicotinamide (BNA ). In Fig. 10(c), the photocatalytic reduction of methyl benzoylformate (MBF) by thiosulfate is described in the presence of the porphyrin ZnTPPS and the mediator quinolinium-3-carboxiamide (DCA ) [107]. This sequence of reactions occurs only in micelles such as those formed by hexadecyl-trimethylammonium bromide, which contain in the interior the ultimate donor acceptor. Finder illumination, ZnTPPS photoreduces DCA to DCQ, which is subsequently extracted into the micelle core. Within the microenvironment, DCA is regenerated via reduction of MBF, while the oxidized porphyrin is reduced by thiosulfate outside the micelle. 

By making the Au nanorods liom hydrophilic to hydrophobic, the nanorods can be made to self-assemble on a substrate by simple evaporation (63). Au nanorods prepared using hexadecyl trimethylammonium bromide are hydrophilic. But they can be made hydrophobic by treating them with mercaptopropyltrimethoxysilane and octadecyltrimethoxy silane. Depending on the concentration of the nanorods in the solution, they assemble either parallel to the substrate (at low concentration) or perpendicular to the substrate (at higher concentration). Nanorod arrays can also be prepared by electrochemieal self-assembly on substrates (64). For example, Mn, Co doped ZnO nanorod arrays on Cu substrates have been prepared by electrochemical self-assembly... 

DSC studies have also been undertaken to investigate the effect of iontophoretic transport of the P-blocker, propranolol hydrochloride on the lipid bilayers of the stratum comeum, pre-treated by two penetration enhancers, sodium lauryl sulfate (NaLS) and hexadecyl trimethylammonium bromide (CTAB). DSC results indicated that NaLS was included into the intercellular lipids during iontophoresis and also showed a slight decrease in the two higher transitions in the SC. Lowering of these lipid endotherms is an indication that the bilayer has increased in fluidity. In the case of CTAB, DSC revealed an increase in the initial skin transition, attributed to the insertion of CTAB into the lipids responsible for this transition. However, pre-treatment of the SC with NaLS proved to be successful in enhancing the flux of propranolol hydrochloride across the SC, while this was not the case for CTAB [17]. 

The preliminary treatment of the nanofiller to make it compatible is carried out with a substance having an affinity for both the montmorillonite and the chosen polymer, e.g., cetyl pyridinium chloride or bromide, hexadecyl trimethylammonium bromide, 7V-[4-(4 -aminophenyl)]phenyl phthalimide, /i-aminobenzoic acid hydrochloride, or a combination of octadecylamine hydrochloride and stearic acid. 

Solvation of the head group has two effects on the adsorbed surfactant molecules one is the penetration depth of the ionic head group into the aqueous phase and the other surface roughness. For example, neutron reflection studies have found a difference in the penetration depth of the ionic head groups of SDS and hexadecyl-trimethylammonium bromide (HDTAB) at the air/water interface [50]. The measured separation between the position of the ionic head group and that of the mean position of the aqueous interface is (7.5 0.1) A for SDS and (8.0 0.1) A for HDTAB. These results are found to be independent of the structure of the adsorbed layer. 

Ultrasonic relaxations of tetradecyl- and hexadecyl-trimethylammonium bromide in the presence of n-pentanol are reported. Only one relaxation time is observed, assumed to be dissociation of n-pentanol from the micelle. The rate constant at zero concentration is 1.8xl0 s two orders of magnitude smaller than the value obtained for an ion of comparable size. 

Pharmaceutical preparations containing riboflavin have been analyzed by TLC using concentrated ethanolic extracts on silica gel plates developed in butanol-benzene-acetic acid-water (8 7 S 3) or butanol-acetic acid-water (9 4 5) (7). Foods, tissue samples and urine each require particular methods of sample preparation and these, together with a number of solvent systems have been reviewed (8). A darkroom is required for sample preparation and chromatography of flavins to prevent photolytic degradation. The fluorescent property of flavins provides a convenient means of detection and spots have been located under radiation at 254 and 366nm (4). HPTLC followed by fiberoptic fluorimetry has been used to quantitate riboflavin in vitamin mixtures and can detect 48-320 ng (6). Recently, a method has been described using mixed-layer plates of GDX-102 and silica gel G (1 1) precoated with hexadecyl-trimethylammonium bromide developed in 60-70% ethanol (9). 

Lopez, R, Venditti, F., Giuseppe Cinelli, G., Ceglie, A. 2006. The novel hexadecyl-trimethylammonium bromide (CTAB) based organogel as reactor for ester synthesis by entrapped Candida rugosa lipase. Proc. Biochem. 41, 114-119. 

FIGURE 4.46 Film rupture probability caused by PTFE ( ) and PDMS-treated glass (O) rods as function of advancing contact angle for films prepared from various aqueous surfactant solutions (hexadecyl trimethylammonium bromide, Triton X-100, and sodium dodecylbenzene sulfonate). (Reprinted from J. Colloid Interface ScL, 127, Frye, G.C.C., Berg, J.C., 222. Copyright 1989, with permission from Elsevier.)... 

PU, polyurethane OMT, organoclay modified with hexadecyl-trimethylammonium bromide MPP, melamine polyphosphate. 

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