Butylammonium hydroxide

The method of choice for determining carboxyl groups in lignin is based on potentiometric titration in the presence of an internal standard, /)-hydroxybenzoic acid, using tetra- -butylammonium hydroxide as a titrant (42). The carboxyl contents of different lignins are shown in Table 6. In general, the carboxyl content of lignin increases upon oxidation. 

Water samples showing contamination by phenols are best examined by extracting the phenol into an organic solvent tri-n-butyl phosphate is very suitable for this purpose. Photometric measurements can be carried out on the extract, and the requisite alkaline conditions are achieved by the addition of tetra-n-butylammonium hydroxide. 

Tetra-n-butylammonium hydroxide (0.1 M solution in methanol). Prepare an anion exchange column using an anion exchange resin such as Duolite A113 or Amberlite IRA-400, convert to the hydroxide form and after washing with water, pass 300-400 mL of methanol through the column to remove water (see Section 7.2). 

Prepare an alkaline solution of the phenol concentrate by placing 4.0 mL of a tri-n-butyl phosphate layer in a 5 mL graduated flask and then adding 1.0 mL of the tetra-n-butylammonium hydroxide do this for each of the four solutions. The reference solution consists of 4 mL of the organic layer (in which the phenol is undissociated) plus 1 mL of methanol. Measure the absorbance of each of the extracts from the four test solutions and plot a calibration curve. 

Determination of organic compounds. The application of photometric titrimetry to organic compounds may be exemplified by the titration of phenols. This can be carried out by working at the /max value (in the ultraviolet) for the phenol being determined (see Section 17.50). It has been shown that by titrating with tetra-n-butylammonium hydroxide and using propan-2-ol as solvent, it is possible to differentiate between substituted phenols.24... 

Valproic acid can be potentiometrically titrated with standardized 0.1 N tetra-n-butylammonium hydroxide in chlorobenzene using a modified glass-calomel electrode system, in which 1.0 M aqueous tetra-n-butylammonium chloride has been substituted for potassium chloride, and employing acetone as the sample solvent. 

Alkylation of the more acidic hydrazo [25] and triazene [26] systems proceeds readily under liquiddiquid two-phase conditions, using tetra-n-butylammonium hydroxide and benzyltriethylammonium chloride, respectively, as the catalysts (Tables 5.5 and 5.6). 

The ruthenium tetroxide dioxide catalytic system is effective for the oxidation of alkanols, although it will also react with any alkene groups or amine substituents that are present. The catalyst can be used in aqueous acetonitrile containing tetra-butylammonium hydroxide with platinum electrodes in an undivided cell Primary alcohols are oxidised to the aldehyde and secondary alcohols to the ketone [30]. Anodic oxidation of ruthenium dioxide generates the tetroxide, which is the effective oxidising agent. 

Tris(tetra-n-buty (ammonium) hydrogen pyrophosphate, 1(ihC4H,)4N]3HP207 (1). Mol. wt. 417.42. The salt is prepared by treatment of Na2H,P,07 (Stauffer) with an acidic ion-exchange resin and then with tetra-n-butylammonium hydroxide. 

This difference in kinetics was exploited to develop a procedure to determine free and reversibly bound sulfite in food. The mobile phase consisted of an aqueous solution of 0.05 M tetra-butylammonium hydroxide adjusted to the desired pH by the addition of glacial acetic acid (34). Fluorimetric detection is also possible, because a reaction of the formaldehyde-bisulfite complex with 5-aminofluorescein gives a nonfluorescent product. The sulfite is measured indirectly by its suppresion of the fluorescence of the reagent (31). This method is applicable to the determination of S02 at > 10 ppm and is not applicable to dark-colored foods or ingredients where SO, is strongly bound, e.g., caramel color. This method does not detect naturally occurring sulfite. Sulfur dioxide is released by direct alkali extraction. 

Measurements with Nile Red were ineffective in measuring the solvent strength of even pure bases (10). Measurements with tertiary systems containing less than 1 % t-butylammonium hydroxide in methanol showed no difference from methanol/carbon dioxide mixtures. 

UV-254 ran M- Bondapak C g methanol water (20 80), 0.05 M tetra-butylammonium hydroxide, H3PO4 pH adjustment 6.1 94... 

Butyl derivatives make possible the resolution of compounds the methylation of which lead to the same derivatives [518]. They were prepared in an analogous manner, by injection of substrates with a 25% methanolic solution of tetra-n-butylammonium hydroxide into the injection port heated at 270°C. The analysis can be performed on 3% OV-17 at 220°C Fig. 5.31 illustrates an example of the separation of several barbiturates in the form of methyl and butyl derivatives. Mephobarbital and phenobarbital, which being methylated give rise to the same compound, could be resolved after their conversion into butyl derivatives in addition, the different retention times of the derivatives could be utilized for the identification of barbiturates. 

A series of variously substituted chloro-androstanes (17 examples), bromo-androstanes (14 examples), and amino-androstanes (29 examples) prepared from the corresponding alcohols and oximes has been described.65 It was noted during the course of this work that all ring A, B, or C oximes were reduced by lithium aluminium hydride to yield over 90% of the corresponding axial amine, except at C-3 where 65% of the equatorial amine was isolated. This is in line with the lithium aluminium hydride reduction of 5a-cholestan-3-one where the equatorial hydroxy-steroid predominates. The observation was also made that when 3/8-, 7/3-, and 16/3-tosy oxy-5a-androstanes are heated with tetra-n-butylammonium hydroxide in... 

The procedure described below was developed by Pobiner (1983) and consists of the nonaqueous potentiometric titration of lignin with tetra-n-butylammonium hydroxide in the presence of an internal standard, p-hydroxybenzoic acid. As is true also for conductometric titrations of lignin (see Chap. 7.7), phenolic hydroxyl and sulfonic acid groups may be coincidentally determined by this procedure. 

Stir the solution of pyrophosphoric acid (obtained in step 1) in an ice bath and add a 10% solution of tetra-/7-butylammonium hydroxide dropwise until pH 7.3 is reached (note use a pH meter). This will be around 50 mL (for methylenebisphosphonic acid and difluoromethylenebisphosphonic acid, the solutions should be titrated to pH 10 and 7.3, respectively). 

The iridium complex 240 reacts with 2equiv of tetra- -butylammonium hydroxide to give the sulfoxide 252 and the methyl ketone 253 in 23% and 37% yields, respectively <2000CCR63>. The mechanism shown in Scheme 77 has been proposed. 

Tetra-n-butylammonium octamolybdate, [(C4Hq)4N]4Mo8026. Mol. wt. 2153.39. The amine salt is prepared in 80% yield by reaction of sodium molybdate, Na2Mo04 2H20 (Alfa), with a 40% solution of tetra-n-butylammonium hydroxide in a ciircfully controlled ratio (cf. Klemperer and Shum ). 

Table 6). Where the expense of tetra-n-butylammonium hydroxide is a consideration, or in cases where the product carboxylic acid is poorly soluble in ether (making extractive removal of tetra-n-butylammonium salts difficult), an alternative procedure employing sodium hydroxide in a mixture of water, methanol, and ferf-butyl alcohol can be used. The mechanism of the base-induced hydrolysis reaction is believed to involve initial rate-limiting intramolecular N- O acyl transfer, followed by rapid saponification of the resulting (3-amino ester. ... 

Electrochemical methods for the reduction of aromatic substrates utilizing ammonia and amines as solvents with lithium salts as electrolytes have been successful. Toluene was reduced to the 2,5-dihydro derivative in 95% yield in methylamine-lithium chloride if an undivided cell was used, while a 53 47 mixture of 3- and 4-methylcyclohexenes was formed in a divided cell.. Of greater interest, however, are attempts to achieve these reductions in aqueous media. In one experiment utilizing a two-phase mixture of substrate in aqueous tetra-n-butylammonium hydroxide and a mercury cathode, anisole was reduced on a preparative scale (15 g) to its 2,5-dihydro derivative in 80% yield. The optimal temperature for most reductions appeared to be 60 °C and under these conditions, even suspensions of high molecular weight substrates could be successfully reduced, e.g. steroid (226) afforded a >90% chemical yield of (227). Much higher coulombic yields were obtained when a small amount of THE was added to the mixture, however. 

---