Water tetramethylammonium

The exact p R+ value for 20+ could also not be determined by the earlier method. Therefore, dimethyl sulfoxide (DMSO)-water-tetramethylammonium hydroxide (0.011 M) system was used for the measurement. The H scale (Hammett acidity scale) for the system ranges from 12 in water up to 26.2 in... 

Thiol esters of aromatic acids, ArC(0)SR, are cathodically reduced, with fission of the S-CO bond generating the arylcarbonyl radical and thiolate as in Eq. (25) [101]. The thiol may be obtained in good yield [102]—for example, L-cysteine in 83% yield from S-benzoyl-L-cysteine at a mercury cathode in DMF-water-tetramethylammonium chloride. The electroreduction of aryl thioesters [containing -C(0)SR, -C(S)OR, and -C(S)SR functions] has been studied, and some interesting products have been formed [103-105], as in Eqs. (26) through (29). Trithiocarbonates are reduced to the tetraalkyltetrathioethylenes [106]. 

Even cationic species such as the (hydrated) hydrogen ion (H ) can be lured into the hydrophobic silicone films from water medium as long as they contain appropriate additives to allow penetration of the analyte. For instance, Nivens et al. [140,141] have reported fabrication of silicone/ sol-gel films using a hydroxy-terminated poly(dimethyl siloxane (PDMS-OH), tetraethoxysilane (TEOS) and 3-ami-nopropyltriethoxysilane (APTES) mixture in ethanol-water. Tetramethylammonium hydroxide (TMAOH) is added to the mixture to entrap the fluorescent pH indicator dye 8-hydroxypyrene-l,3,6-trisulfonic acid trisodium salt (HPTS) [102], after base-catalyzed polycondensation of the silanes and the PDMS-OH. Silica optical fibers are stripped from their jacket at the distal end and dip-coated with the indicator gel before the end of gelation (24 h). The optical fluorosensor is able to measure between pH 6.0 and 8.5 for 6 months if stored in buffer medium. 

Physical Properties. Most quaternary compounds are soHd materials that have indefinite melting poiats and decompose on heating. Physical properties are determined by the chemical stmcture of the quaternary ammonium compound as well as any additives such as solvents. The simplest quaternary ammonium compound, tetramethylammonium chloride [75-57-0] is very soluble ia water (163) and iasoluble ia nonpolar solvents. As the molecular weight of the quaternary compound iacreases, solubiUty ia polar solvents decreases and solubiUty ia nonpolar solvents iacreases (164—166). For example, trimethyloctadecylammonium chloride [112-03-8] is soluble ia water up to whereas dimethyldioctadecylammonium chloride [107-64-2] has... 

Tetramethylammonium bromide [64-20-0] M 154.1, sublimes with dec >230°. Crystd from EtOH, EtOH/diethyl ether, MeOH/acetone, water or from acetone/MeOH (4 1) by adding an equal volume of acetone. It was dried at 110° under reduced pressure or at 140° for 24h. 

Tetramethylammonium chloride [75-57-0] M 109.6, m >230°(dec). Crystd from EtOH, EtOH/CHCl3, EtOH/diethyl ether, acetone/EtOH (1 1), isopropanol or water. Traces of the free amine can be removed by washing with CHCI3. 

The preparation of 2,6-difluoropyridine in 97% yield from 2,6-dichloropyridine can be accomplished at lower temperatures (150 °C) by using a catalytic amount of tetramethylammonium chloride in dimethyl sulfoxide containing less than 1% water [66]... 

FIG. 2 Cyclic voltammogram of the ferricenium transfer across the water-DCE interface at lOmVs. The electrochemical cell featured a similar arrangement to Fig. 1(b), but the organic phase contained 2mM of ferrocene. Heterogeneous oxidation of Fc occurred in the presence of 0.2mM CUSO4 in the aqueous phase. Supporting electrolytes were lOmM 02804 and lOmM BTPPATPBCl. The transfer of the standard tetramethylammonium (TMA+) under the same condition is also superimposed. 

FIG. 9 Upper potential values, a.sds lower potential values, b.sds of the first oscillation at the interface between phases o and wl of the octanol membrane (A), interfacial potential of a two-phase octanol-water system in the absence of SDS, c.sds (B) and those in the presence of 10 mM SDS (in the case of inorganic electrolyte, 1 mM), d.sds (C)- TMACI tetramethylammonium chloride TEACI tetraethylammonium chloride TPACI tetrapropylammonium chloride TBACI tetra-butylammonium chloride AcNa sodium acetate PrNa sodium propionate, BuNa sodium n-butyrate VaNa sodium w-valerate. (Ref 27.)... 

A PRP -1 (Hamilton Reno, NV) reversed phase column was coated with cetylpyridinium and eluted with tetramethylammonium salicylate acetoni-trile water.89 The separation was comparable to that observed on conventional ion exchange. Coated phases were also used to separate oxalate complexes of manganese, cobalt, copper, and zinc.90 Reversed phase silica supports were coated with poly(N-ethyl-4-vinylpyridinium bromide), poly(dimethydiallylammonium chloride), poly(hexamethyleneguanidinium... 

At this point the hygroscopic potassium salt may be isolated and dried, or, more conveniently, the potassium salt may be dissolved in water and the carborane anion precipitated with one of a variety of large cations, such as the rubidium, cesium, tetramethylammonium, or trimethylammonium ions. The tri-methylammonium salt of the carborane anion is useful because it is readily purified by recrystallization from water and may be easily converted in solution to salts containing other counterions. ... 

The KB9C2H10(CH3)2 recovered from the ethanol solution is dissolved in 150 ml. of water, and a solution of 22 g. of trimethylammonium chloride in 100 ml. of water is added slowly with vigorous stirring. The precipitated salt is isolated by filtration, washed once with 50 ml. of cold water, and dried in vacuum over phosphorus(Y) oxide. The yield of (CH3)3NHB9C2Hio-(CH3)2 is 37.8 g. (98%). To purify the salt by crystallization, a boiling solution of 38 g. of the salt in 2 1. of water is allowed to cool slowly to 0°. Eighty per cent of the material is recovered in the first crop. Successive crops of the trimethylammonium salt may be obtained, or the anion may be recovered as the less soluble tetramethylammonium salt by addition of an aqueous solution of tetramethylammonium chloride to the mother liquor. The tetramethylammonium salt may be recrystallized from an ethanol-water solution. 

Kowalska M, Gtiler H, Cocke DL (1994) Interactions of clay minerals with organic pollutants. Sci Total Environ 141 223-240 Kukkadapu RK, Boyd SA (1995) Tetramethylphosphonium-smectite and tetramethylammonium-smectite as adsorbents of aromatic and chlorinated hydrocarbons - effect of water on adsorption efficiency. Clays Clay Miner 43 318-323... 

Laird DA, Barriuso E, Dowdy RH, Koskinen WC (1992) Adsorption of atrazine on smectites. Soil Sci Soc Am J 56 62-67 LeBaron PC, Wang Z, Pinnavaia TJ (1999) Polymer-layered silicate nanocomposites an overview. Appl Clay Sci 15 11-29 Lee J-F, Crum JR, Boyd SA (1989) Enhanced retention of organic contaminants by soil exchanged with organic cations. Environ Sci Technol 23 1365-1372 Lee J-F, Mortland MM, Boyd SA, Chiou CT (1989a) Shape-selective adsorption of aromatic molecules from water by tetramethylammonium-smectite. J Chem Soc Faraday Trans I 8 2953-2962... 

Tetramethylammonium hydroxide, TMAH, (Fluka Chemicals) was diluted with distilled water from a 25 wt % aqueous solution. In all cases the diazonaphthoquinone dissolution inhibitor used was Fairmont Positive Sensitizer 1009 (Fairmont Chemical Company). The syntheses of the PDMSX oligomers and novolac-PDMSX block copolymers have already been reported (11). The dimethylamine terminated poly(dimethyl siloxane), =510 g/mole (Petrarch), was used as the PDMSX component or to prepare higher molecular weight analogs. 

The resist was exposed with an in-house i-line reduction projection aligner or a 600-W Xe-Hg lamp (Cannard Hanovia) in conjunction with a UVD2 band pass filter (Toshiba glass Co.). After removing the top layer by rinsing in water, the resist was developed with a 2. 38 wt% tetramethylammonium hydroxide aqueous solution. 

Wallerberg et al. (1971) conducted the reaction of imidazole and PNPA in acetonitrile containing 1 M water and evaluated the influence of added tetramethylammonium benzoate. The observed rate constant is given by (27) which indicates the contribution of general-base catalysis. Since k2 (1.0 M-2... 

Rate enhancements for these types of reaction have been reported to be as high as 200-fold, and the selectivity of the reaction was found to be very substrate dependent. These reactions must be conducted in dipolar aprotic solvents in the absence of water. Although tetramethylammonium chloride is too polar to find widespread application as a phase transfer agent, it has good thermal stability, and this, combined with its low cost, has resulted in its large scale industrial use in phase transfer catalysed aromatic nucleophilic fluorinations. 

Solid lithium aluminium hydride can be solublized in non-polar organic solvents with benzyltriethylammonium chloride. Initially, the catalytic effect of the lithium cation in the reduction of carbonyl compounds was emphasized [l-3], but this has since been refuted. A more recent evaluation of the use of quaternary ammonium aluminium hydrides shows that the purity of the lithium aluminium hydride and the dryness of the solvent are critical, but it has also been noted that trace amounts of water in the solid liquid system are beneficial to the reaction [4]. The quaternary ammonium aluminium hydrides have greater hydrolytic stability than the lithium salt the tetramethylammonium aluminium hydride is hydrolysed slowly in dilute aqueous acid and more lipophilic ammonium salts are more stable [4, 5]. 

---