Tetrabutylammonium ,

Besides the well-known lower basicity of ethanol, these data illustrate the greater acidity of benzoxazolium compared with benzothiazolium. The relative pK. values of the quaternary salts obtained in acetonitrile when treated with tetrabutylammonium hydroxide are 18.3 and 17.6, respectively (25). Those of 2-methyl 4-phenyl thiazolium and 2.4-dimethyl thiazolium are 20.5 and 21.8 under the same conditions (25). 

This experiment focuses on developing an HPLG separation capable of distinguishing acetylsalicylic acid, paracetamol, salicylamide, caffeine, and phenacetin. A Gjg column and UV detection are used to obtain chromatograms. Solvent parameters used to optimize the separation include the pH of the buffered aqueous mobile phase, the %v/v methanol added to the aqueous mobile phase, and the use of tetrabutylammonium phosphate as an ion-pairing reagent. 

In the 1,6-elimination of j -trimethy1si1y1methy1henzy1trimethy1 ammonium iodide with tetrabutylammonium fluoride, yields as high as 56% have been reported (18). The starting materials are not readily accessible, however, and are cosdy. 

A brief review has appeared covering the use of metal-free initiators in living anionic polymerizations of acrylates and a comparison with Du Font s group-transfer polymerization method (149). Tetrabutylammonium thiolates mn room temperature polymerizations to quantitative conversions yielding polymers of narrow molecular weight distributions in dipolar aprotic solvents. Block copolymers are accessible through sequential monomer additions (149—151) and interfacial polymerizations (152,153). 

An acidimetric quantitative determination is based on treatment of the hydantoia with silver nitrate and pyridine ia aqueous solution. Complexation of the silver ion at N-3 Hberates a proton, and the pyridinium ions thus formed are titrated usiag phenolphthaleia as an iadicator. In a different approach, the acidity of N-3—H is direcdy determined by neutralization with tetrabutylammonium hydroxide or sodium methoxide ia dimethylformarnide. 

Tetrabutylammonium benzoate has been used as a catalyst for the polymerization of PO over the temperature range 40—108°C and the yield of polymer was typically low (2—78%) a large amount of unsaturation was present due to chain transfer (95). When synthetic hydrotalcite,... 

Pha.se-Tra.nsfer Ca.ta.lysts, Many quaternaries have been used as phase-transfer catalysts. A phase-transfer catalyst (PTC) increases the rate of reaction between reactants in different solvent phases. Usually, water is one phase and a water-iminiscible organic solvent is the other. An extensive amount has been pubHshed on the subject of phase-transfer catalysts (233). Both the industrial appHcations in commercial manufacturing processes (243) and their synthesis (244) have been reviewed. Common quaternaries employed as phase-transfer agents include benzyltriethylammonium chloride [56-37-17, tetrabutylammonium bromide [1643-19-2] tributylmethylammonium chloride [56375-79-2] and hexadecylpyridinium chloride [123-03-5]. 

The /-butyldimethylsilyl group introduced by TBDMIM has a number of advantages in protecting alcohols (6). The sdylated alcohol hydroly2es more slowly than an alcohol sdylated with TMS by a factor of 10 . The sdyl ether is also stable to powerful oxidi2ing and reducing agents, but it can easily be removed by aqueous acetic acid or tetrabutylammonium fluoride in tetrahydrofuran. 

Formation of Ethers. Very high ether yields can be obtained from alcohols and phenols with dialkyl sulfates in CH2CI2 and concentrated NaOH—tetrabutylammonium chloride at room temperature or slightly elevated temperature within 1—5 h (18). Using excess aqueous caustic—N(C4H2)4HS04, unsymmetrical aUphatic ethers can be prepared with alkyl chlorides at 25—70°C in 3—4 h (19) (see Ethers). 

The crown ethers and cryptates are able to complex the alkaU metals very strongly (38). AppHcations of these agents depend on the appreciable solubihty of the chelates in a wide range of solvents and the increase in activity of the co-anion in nonaqueous systems. For example, potassium hydroxide or permanganate can be solubiHzed in benzene [71 -43-2] hy dicyclohexano-[18]-crown-6 [16069-36-6]. In nonpolar solvents the anions are neither extensively solvated nor strongly paired with the complexed cation, and they behave as naked or bare anions with enhanced activity. Small amounts of the macrocycHc compounds can serve as phase-transfer agents, and they may be more effective than tetrabutylammonium ion for the purpose. The cost of these macrocycHc agents limits industrial use. 

Specifications, Analysis, and Toxicity. Dicyandiamide is identified quaHtatively by paper chromatography and quantitatively by ultraviolet spectrometry of the chromatogram. More commonly, total nitrogen analysis is used as a purity control or the dicyandiamide is converted by hydrolysis to guanylurea, which is determined gravimetrically as the nickel salt (50). Methods based on the precipitation of silver dicyandiamide picrate are sometimes used (51). Dicyandiamide can also be titrated with tetrabutylammonium hydroxide ia pyridine solution. Table 4 gives a typical analysis of a commercial sample. Dicyandiamide is essentially nontoxic. It may, however, cause dermatitis. 

Bromine electrogeneration was carried out from tetrabutylammonium bromide in 0,1 M NaClO acetonitrile solution with 100 % current yield. 

Bis-(tetrabutylammonium) dichromate [56660-19-6] M 700.9, m 139-142°. Wash with water and dry in a vacuum. Crystallises from hexane (m 79-80°). [Synth Commun 10 75 1980.] (Possible CARCINOGEN). 

Tetrabutylammonium borohydride [33725-74-5] M 257.3, m 128-129 . Purified by recrystn from EtOAc followed by careful drying under vacuum at 50-60°. Samples purified in this way showed no signs of loss of active H after storage at room temperature for more than 1 year. Nevertheless samples should be stored at ca 6° in tightly stoppered bottles if kept for long periods. It is soluble in CH2CI2. [J Org Chem 41 690 1976 Tetrahedron Lett 3113 1972.]... 

Tetrabutylammonium chlorochromate [54712-57-1 ] M 377.9, m 184-185 . Recrystd EtOAc-hexane. IR v 920cm in CHCI3 [Synthesis 749 1983]. Powerful oxidant. 

Boujlel and Simonet used an electrochemical method to prepare a group of similar compounds, including compound ]5, shown in Eq. (3.41). In a typical case, benzil was reduced in DMF solution at the dropping mercury electrode in the presence of tetrabutylammonium iodide, used in this case as a supporting electrolyte rather than phase transfer catalyst. In the presence of diethylene glycol ditosylate, compound 15 (mp 77— 78°) was isolated in 10% yield. Using the same approach, acenaphthenedione was reduc-tively cyclized with triethylene glycol ditosylate to afford the product (mp 84—85°, 42% yield) shown in Eq. (3.42). 

Early workers using anhydrous tetrabuCylammonium fluonde (TBAF) may have actually used mixtures of TBAF and tetrabutylammonium bifluoride It IS known that excessive drying at 77 °C in a vacuum below 2 torr (1 torr = 133 322 Pa) produces the bifluoride salt [20] TBAF can be obtained by drying commer... 

Difluoromethoxy-2-chloro-l,l,l-trifluoroethane and potassium fluoride produce 2-difluoromethoxy-1,1,1,2-tetrafluoroethane [50] The yield of the latter reaction is improved by adding a phase transfer catalyst or crown ether, tetra-methylammonium chlonde, tetrabutylammonium chloride, or 18-crown-6 with a solvent like sulfolane can be used for this purpose [5/] (equation 32)... 

Tetrabutylammonium fluoride trihydrate (Aldnch) is heated in a round-bottom flask with magnetic stirring at 40-45 C under vacuum (<0.1 mm of Hg) After several hours, the sample liquefies. Heating is continued until the sample loses 20% of its original weight (usually ca 48 h). The resulting anhydrous TBAF (singlet at -99 ppm, F NMR) contains 0 1-03 molar equivalent of water (by NMR) and ca 10% tetrabutylammonium bifluoride (a doublet at -146 ppm, (J = 123 Hz, F NMR) This oil must be used immediately. 

Epoxides are regio- and stereoselectively transformed into fluorohydrins by silicon tetrafluoride m the presence of a Lewis base, such as diisopropyleth-ylamme and, m certain instances, water or tetrabutylammonium fluoride The reactions proceed under very mild conditions (0 to 20 C in 1,2-diohloroethane or diethyl ether) and are highly chemoselective alkenes, ethers, long-chain internal oxiranes, and carbon-silicon bonds remain intact The stereochemical outcome of the epoxide ring opening with silicon tetrafluoride depends on an additive used, without addition of water or a quaternary ammonium fluoride, as fluorohydrins are formed, whereas m the presence of these additives, only anti opening leading to trans isomers is observed [17, 18] (Table 2)... 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

Various sources of fluoride ion have been investigated, of which highly nucleophilic tetraalkylammonium fluorides ate the most effective Thuf, fluoro alkyl halides and N (fluoroalkyl)amines are efficiently synthesized by treatment of the corresponding trifluoromethanesulfonic esters with tetrabutylammonium fluoride trihydrate in aprotic solvents [5fl] (equation 34) The displacement reactions proceed quantitatively at room temperature within seconds, but tail with hydrogen fluoride-pyridine and give reasonable yields only with hydrogen fluo ride-alkylamine reagents... 

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