Tetrabutylammonium hydroxide

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). 

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. 

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. 

Tetrabutylammonium hydroxide 716 Tetraphenylarsonium chloride, 482 Thallium, D. of as thallium(I) chromate,... 

Griffin and Albaugh [102] describe a procedure whereby the neutral AOS product is converted to the parent acids by cation exchange and then titrated potentiometrically. A dilute aqueous solution of AOS is passed through cationic ion exchange resin in acid form. The acids are eluted with small portions of water and titrated potentiometrically using tetrabutylammonium hydroxide solution in a solvent mixture of 70 30 benzene/methanol. It is probable that the benzene can be replaced with toluene for safety reasons or that ASTM titration solvent (ASTM D664 toluene/propan-2-ol/water) can be used. 

Disodium glyphosate has been reacted with activated heteroaryl halides, such as 2-chlorobenzothiazole or 2-chlorobenzoxazole 79, in aqueous alcohol at reflux to produce the N heteroaryl glyphosate derivadves 80 (2). Improved yields have often obtained in these reactions using the more soluble bis-quatcmary ammonium salt of glyphosate derived from tetrabutylammonium hydroxide (2). 

The original conditions used amines as solvents or cosolvents. Several other bases can replace the amine. Tetrabutylammonium hydroxide or fluoride can be used in THF (see Entry 1 in Scheme 8.11).163 Tetrabutylammonium acetate is also effective with aryl iodides and EWG-substituted aryl bromides (Entry 2).164 Use of alkenyl halides in this reaction has proven to be an effective method for the synthesis of enynes165 (see also Entries 5 and 6 in Scheme 8.11). 

The generated quinone methide intermediates, during the disassembly, are highly reactive electrophiles and rapidly react with any available nucleophile (methanol or tetrabutylammonium hydroxide under organic solvent conditions). We could not isolate any significant amount of material that derived from the core molecule, probably due to generation of a mixture of compounds by the addition of different nucleophiles to the quinone methide. This molecule acts as an amplifier of a cleavage... 

TBAH Tetrabutylammonium hydroxide TMTD Tetramethylthiuram disulfide... 

Column C-18 mobile phase CH3OH/H2O 50 50 + tetrabutylammonium hydroxide (pH about 7.5). 

Dissolve 0.30 g of niclosamide in 80 mL of a mixture of equal volumes of acetone and methanol. Titrate with 0.1 tetrabutylammonium hydroxide, determining the endpoint potentiometrically. One milliliter of 0.1 M tetrabutylammonim hydroxide is equivalent to 32.71 mg of CnHgCyS O ... 

Similar procedures adopted for the synthesis of TS-1 (the mixed alkoxide method, dissolved titanium method, pre-hydrolysis method, wetness impregnation method, and promoter induced synthesis method) were also used for the synthesis of TS-2. Tetrabutylammonium hydroxide (TBAOH) instead of TPAOH was used as the template (6,7,305-308). 

The alkalimetry in non-aqueous titrations may also be carried out efficiently by using tetrabutylammonium hydroxide along with an appropriate indication... 

Materials Required Benzoic acid 60 mg dimethylbromide 10 ml thymol blue solution (0.3% w/v in methanol) 0.1 N tetrabutylammonium hydroxide. 

Materials Required Chlorthalidone 0.3 g pyridine (dehydrated) 50 ml 0.1N tetrabutylammonium hydroxide. 

Procedure Weigh accurately about 0.3 g and dissolve in 50 ml of dehydrated pyridine. Titrate with 0.1N tetrabutylammonium hydroxide, determining the end point potentiometrically and protecting the solution and titrant from atmospheric carbon dioxide throughout the determination. Perform a blank determination and make any necessary correction. Each ml of 0.1N tetrabutylammonium hydroxide is equivalent to 0.03388 g of q4HuCIN204S. 

The following pharmaceutical substances may be assayed by employing tetrabutylammonium hydroxide either by using a suitable indicator titrimetrically or potentiometrically as given in Table 5.5. 

Diloxanide Furoate 0.3 g Potentiometric determination Each ml of 0.1 N Tetrabutylammonium hydroxide = 0.03282 g of C14HnCl2N04... 

The assay of the aforesaid pharmaceutical substances with tetrabutylammonium hydroxide is on a mole-for-mole basis. As these are monobasic acids in character, therefore, they react quantitatively in a non-aqueous media with the base titrant, employing typical acid-base indicators to detect the end-points. 

Preparation of 0.1 M Tetrabutylammonium hydroxide (1 Litre) Dissolve 40 g of tetrabutylammonium iodide in 90 ml of anhydrous methanol, add 20 g of finely powdered silver oxide and shake vigorously for 1 hour. Centrifuge a few ml of the mixture and test the supernatant liquid for iodides. If a positive reaction is obtained add a further 2 g of silver oxide and shake for 30 minutes. Repeat this procedure until the mixture is free from iodides, filter through a fine sintered-glass filter and wash the reaction vessel and filter with three 50-ml quantities of toluene. Add the washings to the filtrate and add sufficient toluene to produce 1000 ml. Pass dry carbon-dioxide free N2 through the solution for 5 minutes. 

Standardization of 0.1 M Tetrabutylammonium Hydroxide To 10 ml of dimethylformamide add 0.05 ml of a 0.3 % w/v solution of thymol blue in methanol and titrate with the tetrabutylammonium hydroxide solution until a pure blue colour is produced. Immediately add 0.2 g of benzoic acid, stir to effect solution and titrate with the tetrabutylammonium hydroxide solution until the pure blue colour is restored. Protect the solution from atmospheric C02 throughout the titration. The volume of titrant used in the second titration represents the amount of tetrabutylammonium hydroxide required. Each ml of 0.1 M tetrabutylammonium hydroxide Vs is equivalent to 12.21 mg of C7Hg02. 

Scheme 7). The two-fold Diels-Alder cycloaddition of an excess of tetra-phenylcyclopentadienone (13), which is regarded as a first-generation dendron, to 24 in refluxing o-xylene leads to the second-generation benzilic dendron 25. The dendron is isolated as a pale yellow amorphous powder in 91% isolated yield. The Knoevenagel condensation of 25 with 1,3-diphenylacetone (26) to the corresponding cyclopentadienone dendron 27 is achieved in dioxane and in the presence of tetrabutylammonium hydroxide as a base. Like 25, the cyclopentadi-... 

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