Ammonium bromide reagents

Ellman s reagent" + dithionite Synthetic vesicles of dicetyldimethyl-ammonium bromide. Effects of vesicles and fast and slow reaction components separated Moss and Schreck, 1983... 

Two phase reduction (Brust synthesis) This method is usually employed to make organic soluble quantum clusters [8]. This method consists of two steps. The first is the transfer of AuCLi from aqueous to the organic layer by a phase transfer reagent such as tetraoctyl ammonium bromide (TOABr). The next step is the subsequent reduction of AuCU in the presence of suitably selected ligands such as thiols, phosphines, etc. 

Fig. 5. Bromination of phenols and anisols using a quaternary ammonium bromide in combination with nitric acid as bromination reagent. Y is OH and OCH3 for phenols and anisols, respectively. X is H or CH3...

The ammonium bromide, potassium iodide, and sodium acetate were British Drug Houses Analar analytical reagent grade. The potassium acetate was Baker Analyzed crystal reagent grade from J. T. Baker Chemical Co. Owing to the extreme hygroscopicity of some of these salts, they all were dried for at least 72 hours at 120° C immediately prior to each series of experiments. The dried salts then were stored under vacuum over phosphoric pentoxide between each experimental measurement. 

Next, process chemistry for the practical synthesis of 7b (MGS0028) is discussed (Schemes 3.5-3.7) [42-45]. First, the synthesis of key intermediate (+)-29 from racemic acetoxycyclopentene (34) is shown in Scheme 3.5 [43]. The key reaction in this approach was Trost s asymmetric ally lie alkylation reaction of ethyl 2-fluoroacetoacetate with 34, which afforded 35 in high yield and high enantioselectivity, especially when a bulky tetra-n-hexyl ammonium bromide was used as a phase-transfer reagent (89% yield, 94-96%... 

All chemicals were obtained reagent grade from Aldrich Chemical Company. The liquids were passed through a column of Woelm Act. I alumina for purification, and were subsequently dried and storaged over 4A molecular sieves. The cetyltrimethyl-ammonium bromide (CTAB) was twice recrystallized from acetone. 

The diene-Br2 complex is again in equilibrium with the reagents, and nucleophilic attack at carbon can be carried out either by the bromide of the ammonium bromide ion pair, formed at the moment of the electrophilic attack, or by the less nucleophilic pyridine added in excess in the reaction medium. It is noteworthy that this mechanism is characterized by a rate- and product-limiting nucleophilic step which should be quite insensitive to steric hindrance around the double bond. In agreement with a weak influence of the steric effects, pyridinium perbromide reacts in chloroform and tetrahydrofuran with substituted conjugated and non-conjugated dienes to give selectively (>95%) bromine addition to the more alkylated double bond (equation 44). 

Hydroxybenzaldehyde-5-nitro-pyridylhydrazone in the presence cetyltrimethyl-ammonium bromide was used as a reagent for the determination of trace amounts of cobalt [9]. The interference from Pb, Ni " and Cu " could be eliminated after separation of the metal ions on Amberlite lRC-718 resin. 

Dimethyldioctadecyl ammonium bromide (DDAB) can be purchased from Sigma or Avanti Polar Lipids, or formulated with DOPE in Lipofectace reagent (Gibco-BRL). 

The synthesis and characterization of a mesoporous silicoalumino phosphate are given employing typical structure directing reagent viz. cetyltrimethyl ammonium bromide. The Si MAS NMR showed that silicon is found in coordination with 1, 2, 3 and 4 A1 ions through oxygen bridges. The sorption characteristics of this new mesoporous SAPO material are also presented. Keywords Silico aluminophosphate, Mesoporous, ordered molecular arrays, MAS NMR. 

In one study, an arabino-(4-0-methylglucurono)xylan of pine had to be isolated in the pure form without the use of any alkaline reagents. A chlorite holocellulose was extracted with methyl sulfoxide, followed by hot water. The product from the latter extraction was dissolved in water, and a xylan-rich fraction was precipitated by adding cetyltrimethyl-ammonium bromide. When a chlorite holocellulose of spruce was extracted with methyl sulfoxide and then with water, the former extract was richer in xylan, and the latter in glucomannan. ... 

Schullerer et al. developed a method for the enrichment of lOS compounds for aromatic sulfonates from water samples. The sum parameter is based on the principle of ion-pair solid-phase extraction. Analogous to the ion-pair chromatography, a reversed-phase Cjg material is used as adsorbent while tetrabutyl ammonium bromide is used as ion-pairing reagent, as already mentioned in previous chapters. 

The presence of micropores in carbon materials usually facilitates metal dispersion, which does not, however, translate into an increase in the catalytic activity. This may be explained by the blockage of metal nanoparticles in micropores, which are not accessible to reagents [98]. As a consequence, PEMFC specifications require that carbon materials used in PEMFCs comprise a high contribution level of mesopores, but no micropores. The ratio of the surface area of mesopores (the external surface area) to the overall pore area may be characterized by the Actab bet ratio, where Actab is the surface area measured using cetyltrimethyl-ammonium bromide. It has been shown that carbon blacks with a Actab/Abet... 

Materials. The reagents Mo(CO)e, W(CO)6, iodine, tetrapropyl-ammonium bromide, tetrabutylammonium iodide, propionic acid, benzoic acid, pivalic acid, and 1,2-dibromoethane were obtained from commercial sources and used without purification. The solvents chlorobenzene, 1,2-dichloroethane, o-dichlorobenzene, toluene, decahydronaph-thalene (decalin), and cyclohexane were purged 10-30 min with a stream of dry nitrogen prior to use. Acetonitrile was dried over molecular sieves (4A) and also purged with nitrogen prior to use. Benzene used in the preparation of MoW(02CC( 113)3)41 was carefully dried and stored over calcium hydride, then vacuum distilled into the reaction vessel when needed. 

Reissert reaction. The alkylation of Reissert compounds with bcnzylic halides was originally conducted with NaH as base in DMF. Skiles and Cava have examined three more modern systems LDA and HMPT in THF, KOH and a crown ether, and phase-transfer conditions. Of these, the two last systems are clearly superior to the first the phase-transfer system is somewhat superior to the crown ether system, both in yields and economic use of reagents. Cetyltrimethyl-ammonium bromide served as catalyst. 

The oxidation of various sulfides 424 with iodosylbenzene in the presence of catalytic amounts of quaternary ammonium bromides affords the respective sulfoxides 425 in high yields (Scheme 3.171) [521]. The best catalytic effect in this reaction is observed when oxidation is carried out in a nonpolar solvent (toluene, hexane, dichloromethane) in the presence of trace amounts of water and 10 mol% of cetyltrimethylammonium bromide (CTAB). Iodosylbenzene can also be activated in the solid state by pulverization with natural clays or silica gels [522, 523], The oxidation of various alkyl aryl sulfides with (PhIO) supported on natural (montmorillonite, KSF and bentonite clays) as well as cation-exchanged KlO-montmorillonite clays affords sulfoxides in excellent yields. A mechanism involving depolymerization of (PhIO) by the acidic SiOH sites on the clay is proposed for this reaction [522], Organic sulfides are also selectively oxidized to sulfoxides by the solid reagent system PhI(OAc)2-alumina [524], or by Phl(OAc)2 in water in the presence ofKBr [525],... 

CHg),N Cl-, Tetra-ethylammonium chloride, - bromide (Cflg),N F-, (n-C,Hg),NH-Stearyltrimethyl-ammonium chloride Benzyltrimethyl-ammonium chloride, Benzyltriethyl-ammonium -Girard reagent T Pyridinium ethiodide (CHg),NBr-Br2... 

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