Ethylammonium bromide

Cationic accelerants vary in their efficacy [161]. Other types of accelerant have also been evaluated. In one study [162], comparisons were made between tetra-ethylammonium bromide, benzyltriethylammonium chloride, polyfdiallyldimethylammonium chloride) and the diethyldimethylammonium derivative of a benzenesulphonate polyglycol ester. It was found that the cationic polymers had a greater effect than the simple quaternary ammonium compounds of lower molecular mass. This effect was attributed to the capability of the polymers to enter into hydrophobic interaction with the fibre surface. Ethylenediamine has also been found to accelerate the alkaline hydrolysis of polyester [163]. 

One such process utilizes catalytic amounts of anhydrous calcium bromide, magnesium bromide, or tetr ethylammonium bromide at l O-2l0V0, ilM 11M whereas the other employs pyridine, trimethyl-amine, or other tertiary nitrogenous bases 1 Although detailed... 

Key to Figures 16 and 17 1, Pyrazine 2, 2-Methylpyrazine 3, 2,6-Dimethyl-pyrazine 4, Quinoxaline 5, 2-Methylquinoxaline 6,, 4-Diazabicyclo, 2,2 -octane 7, Pyridine 8, Dioxan 9, Tetramethylammonium bromide 10, Tetror ethylammonium bromide 11, Tetrcq>ropylaminonium bromide 12, Tetrabutyl-ammonium bromide 13, n-propanol. 

Fig.3 Coexistence curve of the system tri-methyl-ethylammonium bromide -i- chloroform in the presence of 1% ethanol. The arrow indicates the CP.

Most mechanistic thinking in the area of glycoside synthesis is shaped by a seminal paper by Lemieux et al, in which an array of solvent-separated and intimate ion pairs is invoked, in heroic defiance of Occam s razor . The key discovery was that, whereas tetraacetyl a-D-glucopyranosyl bromide in a mixture of phenol and pyridine gave the p-pyridinium salt exclusively, in anhydrous pyridine anomeric mixtures were produced, and addition of tetra-ethylammonium bromide gave exclusively the a-anomer (Figure 3.38). Similar... 

Larsen, J. W. Magid, L. J., Enthalpies of binding of organic molecules to cetyltrim-ethylammonium bromide micelles. Journal of Physical Chemistry 78, (8), 834-839, 1974. 

Amines react as nucleophiles with alkyl halides in Sn2 reactions, as seen in Section 11.2.1 for the conversion of 21 to 23. This example is repeated, but the isolated product is tertiary amine 38 rather than ammonium salt 23. Displacement of bromide ion by the nucleophilic nitrogen in dimethylamine (22) leads to formation of N,iV-dimethylammonium-l-aminopropane, 23, as described previously. However, this salt is a weak acid, and it is formed in the presence of amine 22, which is a base (Chapter 6, Section 6.4.1) as well as a nucleophile. A simple acid-base reaction occurs between 23 and 22 to generate the neutral amine (N,iV-dimethylaminopropane, 38) along with dim-ethylammonium bromide. This reaction may not be quite as simple as shown, however. 

Propynyl) N-(triphenylphosphoranylidene)henzenamine 1719 (R = H) To Ph3PBr2 (4.22 g, 10.0 mmol) were added amine 1718 (R = H) (1.31 g, 10.0 mmol), anhydrous triethylamine (2.78 mL), and anhydrous benzene (100 mL) under nitrogen atmosphere. The reaction mixture was heated under reflux for 4 h. The white tri-ethylammonium bromide that precipitated was removed by filtration, and the filtrate was concentrated. The residue was purified by column chromatography (silica gel 40-60% diethyl ether in hexanes) to furnish 2.776 g (7.10 mmol, 71%) of 1719 (R = H) as colorless crystals. 

Electroreductions of organic catalysts 9-phenylanthracene (9-PA) and l,2-dicyanobenzene > (1,2-DCB or o-phthalonitrile) were chemically reversible and diffusion controlled at cyclic voltammetric (CV) scan rates between about 0.2 and 50 V/s in aqueous 0.1 M CTAB containing 0.1 M tetra-ethylammonium bromide (TEAB). The anion radicals of 9-PA and 1,2-DCB were stabilized against reaction with proton donors by the cationic micellar... 

Mixtures of europium and ytterbium were determined by Wise and Cokal (199) by controUed-potential reduction of the trivalent ions to the bivalent state at — 1.2 V vs. methanolic Ag-AgBr electrode in anhydrous methanol containing 0.1 n tetra-ethylammonium bromide as supporting electrolyte. Europium is determined by a reduction and re-oxidation procedure similar to that described above and the ytterbium concentration is calculated by difference. 

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