Boronic water complexation

Acetylcyclohexanone. Method A. Place a mixture of 24-6 g. of cyclohexanone (regenerated from the bisulphite compound) and 61 g. (47 5 ml.) of A.R. acetic anhydride in a 500 ml. three-necked flask, fitted with an efficient sealed stirrer, a gas inlet tube reaching to within 1-2 cm. of the surface of the liquid combined with a thermometer immersed in the liquid (compare Fig. II, 7, 12, 6), and (in the third neck) a gas outlet tube leading to an alkali or water trap (Fig. II, 8, 1). Immerse the flask in a bath of Dry Ice - acetone, stir the mixture vigorously and pass commercial boron trifluoride (via an empty wash bottle and then through 95 per cent, sulphuric acid) as fast as possible (10-20 minutes) until the mixture, kept at 0-10°, is saturated (copious evolution of white fumes when the outlet tube is disconnected from the trap). Replace the Dry Ice-acetone bath by an ice bath and pass the gas in at a slower rate to ensure maximum absorption. Stir for 3 6 hours whilst allowing the ice bath to attain room temperature slowly. Pour the reaction mixture into a solution of 136 g. of hydrated sodium acetate in 250 ml. of water, reflux for 60 minutes (or until the boron fluoride complexes are hydrolysed), cool in ice and extract with three 50 ml. portions of petroleum ether, b.p. 40-60° (1), wash the combined extracts free of acid with sodium bicarbonate solution, dry over anhydrous calcium sulphate, remove the solvent by... 

The complexes formed with boron trihalides are decomposed to pyridine by boiling water. Complexes with other Lewis acids behave similarly. 

The acylating reagent may be an acid chloride or an acid anhydride. Symmetrical ketones (—CH2 R = R2) yield only a single regioisomer. Thus acetone or cyclohexanone may be acylated with acetic anhydride in the presence of boron trifluoride-etherate to pentane-2,4-dione and 2-acetylcyclohexanone respectively (Expt 5.102). Both diketones are present in the reaction mixture as boron difluoride complexes [(10) and (11) respectively], from which they may be released by treatment with sodium acetate. Pentane-2,4-dione is appreciably water soluble and is isolated by means of its characteristic copper complex (12). 

Wear nitrile rubber gloves, laboratory coat, eye protection, and, if necessary, a self-contained breathing apparatus. Cover the spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. When the boron trifluoride complex has been absorbed, scoop the mixture into a plastic pail and, in the fume hood, very slowly add the mixture to a pail of cold water. Allow to stand for 24 hours. Test the pH of the solution and neutralize if necessary with sodium carbonate. Decant the solution to the drain. Treat the solid residue as normal refuse.5... 

The authors proposed that the HAT from water was mediated by a boron aqua complex in which the strength of the O-H bond was weakened by 30 kcal mol with respect to non-coordinated water (Scheme 36). 

BF3 HjO and BF3 - 2 H2O, are formed at 25 C in equilibrium with free boron fluoride. In the same paper, the isomerisation of butene-2 by this catalytic mixture was examined kinetically. The rate of isomerisation was found to be proportional to the free BF3 as well as to its water-complex concentration, and to the olefin concentration. No complex between boron fluoride and mcmomer was identified, but in their conclusions the authors noted that a mechanism involving attack of the complex BF3 - H2O the complex butene-BF3 would satisfy the kinetics, but seems to have little else to recommend it . In fact we feel that precisely that mechanism was operative, through an Ad 3 intermediate, the Lewis acid-olefin complex being formed, but as in many other instances being too weak to be detected. In the light of present-day knowledge, this conclusion seems quite acceptable, but twenty years ago it probably seemed far-fetched. In any case, the authors clearly realised this possibility, but were too cautions about proposing it outri t. 

Boron was removed from distilled water by using a column of Dowex-1 (OH -form). For the photometric determination as a boron-curcumin complex, interfering ions were removed on small columns of Dowex-1 (formiate) and Dowex-50 (Na ) For the evaporation and ashing step, calcium hydroxide was used (recovery of one ng ca. 80%). By complexation of bivalent ions with 1,2-diamino-cyclohexane-NJ, N, N -tetra-acetic acid, water samples at pH 5.5 passed through a colunm of Dowex 50 W-X 8 (NH4) for the determination of barium Elution followed with 4 M nitric acid. Particular references for the separation of barium from sodium, calcium and sulfate are given. 

Anthraquinonecarboxamide in its Sj state will photoadd two molecules of water. The photoreactions of diphenylhomobenzoquinones in the presence of amine donors have been studied. 1-Bromo substituted diphenylhomobenzoqui-none irradiated in the presence of triethylamine induces opening of the cyclopropane ring with formation of 2-diphenylmethyl-5-methyl-l,4-benzoquinone, and with dimethylaniline, a mixture of an aminated bicyclic dione and bis(p-dimethyl-aminophenyl)methane is produced. Irradiation of boron difluoride complexes derived from 1,3-diketones can lead to a number of different types of process, in particular exciplex formation and slow cycloaddition. Evidence has now been advanced to suggest that excitation of these complexes leads directly to an exciplex without the participation of an encounter complex, and that this solvolyses to free ions. 

It is unnecessary to isolate the boron trifluoride complex, for the following procedure can also be used. A solution of A-benzylideneaniline (3.6 g) in four equivalents of acetone is cooled in ice, and then boron trifluoride etherate (2.8 g) is added. After being kept for 5 min in ice, this mixture is at once poured on to ice + water (100 ml). The oil that separates soon crystallizes. 

Phosphorus(V) chloride-gallium(III) chloride is a moisture-sensitive white crystalline solid melting at 368 to 371°. It is insoluble in carbon tetrachloride and chloroform, reacts with acetone, and is immediately hydrolyzed by water. In comparison with the corresponding phosphorus (V) chloride-boron chloride complex, it is much more difficult to sublime. Indications are that the structure is ionic, [PCl4]+[GaCl4]-. 

The presence of a small amount of water enhances the efficiency of these Suzuki reactions of alkyl bromides. Thus, if anhydrous K3PO4 rather than K3P04-H20 is used, the cross-coupling proceeds much more slowly. B NMR studies revealed that, in the presence of water, a hydroxy-bound boron ate complex is formed, which was suggested might be the species that participates in the transmetalation step of the catalytic cycle. 

To study the interaction of phenylboronic acids with amines in water, Yatsimirsky et al. used NMR spectroscopy to probe the charged state of the boron when complexing with an amine. At neutral pH ( 7.0), 2-formylphenylboronic acid (2-FPBA) shows two boron resonances at 29.3 and 8.6 ppm. Acidification of the solution to pH 6.5 results in the complete disappearance of the 8.6 ppm peak. Hence, the peak at 29.3 ppm corresponds to the neutral boronic acid FPBA. Increasing the pH of the solution to pH 9.0 shows elimination of the 29.3 ppm signal. This means that the peak at 8.6 ppm corresponds to the anionic boron in 17 (Scheme 2.9). To deduce... 

Considering Scheme 7 we define the formation of the diol boronate anion complex as Aitet and the formation of the diol boronic acid complex as ATtrig, where it is observed that ATtet > ATtrig. For instance, the logarithm of these constants for phenylboronic acid binding fructose in 0.5 M NaCl water is log ATtet=3.8 whereas log ATtrig < 1.4. This difference in the value of the binding... 

Sulfonation of aromatic hydrocarbons with sulfuric acid is cataly2ed by hydrogen fluoride or, at lower temperatures, by boron trifluoride (144). The products obtained are more uniform and considerably less sulfuric acid is needed, probably because BF forms complexes with the water formed ia the reaction, and thus prevents dilution of the sulfuric acid. 

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