Reaction with boric acid

Reaction with boric acid and hydrofluoric acid forms potassium tetrafluo-roborate, KBF4 ... 

This reagent, stable in water in slightly alkaline conditions, is ideal for reducing sugars. The aldehyde function is reduced to a primary alcohol and the ketone function to a mixture of secondary alcohol epimers. The simplest treatment after reduction consists in eliminating the sodium on a cation exchanger column, then reaction with boric acid in the form of volatile methyl borate by co-evaporation with methanol. The alditol is recovered by evaporation of the solvent to dryness or lyophilization. 

HOCHjCHjOH Reaction with boric acid 5.3.2.2.4 CjHjO S... 

PbSO HjO S Pb Violent reaction with boric acid potassium. Reacts, possibly violently, with carbon dust, finely divided aluminum, magnesium, zirconium. High heat and fire decon osition products include toxic fumes of sulfur and lead oxides. Probable human carcinogen. On small fires, use dry chemical powder (such as Purple-K-Powder), foam, or COj extinguishers. 

Dibenzylphosphoric acid and dicyclohexylcarbodi-imide were used to generate tetrabenzyl phosphate. This could then be reacted with 2,3-isopropylidene-glycerol in the presence of imidazole to yield 2,3-iso-propylidene-5n-glycerol-l-dibenzyl phosphate. De-benzylation of the latter was carried out with barium iodide and the barium salt was converted to the silver salt which was reacted with 3-iododeoxy-l-oleoyl-2-palmitoyl-5n-glycerol. The fully protected phosphatidylglycerol was debenzylated, followed by reaction with boric acid in trimethyl borate which effected removal of the isopropylidene group (Rosenthal, 1975). Yields of 30% are obtained (Slotboom and Bonsen, 1970). 

Sodium Fluoroborate. Sodium fluoroborate is prepared by the reaction of NaOH or Na2C02 with fluoroboric acid (51), or by treatment of disodium hexafluorosihcate with boric acid. 

Diphenylamine can also be produced by passing the vapors of aniline over a catalyst such as alumina, or alumina impregnated with ammonium fluoride (17). The reaction is carried out at 480°C and about 700 kPa (7 atm). Conversion per pass, expressed as parts diphenylamine per 100 parts of reactor effluent, is low (18—22%), and the unconverted aniline must be recycled. Other catalysts disclosed for the vapor-phase process are alumina modified with boron trifluoride (18), and alumina activated with boric acid or boric anhydride (19). 

Boric oxide is an excellent Lewis acid. It coordinates even weak bases to form four-coordinate borate species. Reaction with sulfuric acid produces H[B(HSO 4] (18). At high (>1000° C) temperatures molten boric oxide dissolves most metal oxides and is thus very corrosive to metals in the presence of oxygen. 

Alcohols react with boric acid with elimination of water to form borate esters, B(OR)3. A wide variety of borate salts and complexes have been prepared by the reaction of boric acid and inorganic bases, amines, and heavy-metal cations or oxyanions (44,45). Fusion with metal oxides yields... 

Rapid procedure Dry over anhydrous K2CO3 for 24h, followed by further drying for 24h over 3A molecular sieves or boric anhydride, followed by distn. Alternatively, stir over P2O5 (5% w/v) for 24h then distil. However this last method is not suitable for use in reactions with very acid sensitive compounds. 

Discussion. Minute amounts of beryllium may be readily determined spectrophotometrically by reaction under alkaline conditions with 4-nitrobenzeneazo-orcinol. The reagent is yellow in a basic medium in the presence of beryllium the colour changes to reddish-brown. The zone of optimum alkalinity is rather critical and narrow buffering with boric acid increases the reproducibility. Aluminium, up to about 240 mg per 25 mL, has little influence provided an excess of 1 mole of sodium hydroxide is added for each mole of aluminium present. Other elements which might interfere are removed by preliminary treatment with sodium hydroxide solution, but the possible co-precipitation of beryllium must be considered. Zinc interferes very slightly but can be removed by precipitation as sulphide. Copper interferes seriously, even in such small amounts as are soluble in sodium hydroxide solution. The interference of small amounts of copper, nickel, iron and calcium can be prevented by complexing with EDTA and triethanolamine. 

A cooling, lubricating, and cleaning agent for use by the metalworking industry has been patented. It is produced by the condensation reaction of an excess diethanolamine or monoethanolamine with boric acid and an ether carboxylic acid or mixtures of ether carboxylic acids and fatty acids [46]. An advantage of these products is that they prevent the deposition of lime soaps. 

Identical conditions for the synthesis of a-hydroxyalkylphosphines and for borylation make it possible to combine the formation of a-hydroxyalkylphosphines and their interaction with boric acids derivatives. As a rule, in all the examples cited below, there is one single course of reaction without any by-products. Thus, diphenylboryloxyalkyl(imidoyl)phos-phines (114) [Eq. (71)], ammonium 1,3,2,5-dioxaborataphosphorinanes... 

The reaction of phenylphosphine with boric acid and 2 mol of salicylic aldehyde was carried out in the presence of pyridine with azeotropic removal of water and gave rise to the complex of pyridine with B(III) (116), bonded to three oxygen atoms (87IZV2118 89IZV946) [Eq. (75)]. 

An important feature of saturated oxazolo[3,4- ]pyridines is their easy epimerization at the aminal C-l stereocenter. A quite explicit example has been reported by Moloney et al. and is depicted in Scheme 46. The reaction between lactam 157 and benzaldehyde produces a mixture of hexahydro-oxazolo[3,4- ]pyridines, the kinetic product 158 being the major one. Equilibration of the mixture with boric acid allows the ratio of diasteroisomers to be reversed since /rarcr-oxazolidine 159 is now the major product <1998TL1025> the equilibration of epimeric oxazolidines via ring-chain tautomerism has been investigated in detail and explains the epimerization observed for some hexahydro-oxazolo[3,4-4]pyridines <1993JOC1967>. 

Boric acid is produced from borax, colemanite, or other inorganic borates by reaction with sulfuric acid or hydrochloric acid, and cooling the solution to proper temperature ... 

Reaction with oxalic acid or boric acid yields phosphoryl chloride ... 

An important class of borate esters is the anionic spirocyclic esters, shown in Eq. (7). The reaction of two molar equivalents of 1,2- or 1,3-diol with boric acid to form such spirocyclic esters is accompanied by dramatic decrease in pH, a consequence of the kinetic stability of these esters. This reaction... 

Reactions 4 to 6. In the hydrogen + oxygen reaction in boric acid-coated vessels at about 500°C. the mutual reaction of HOO competes with H-abstraction from H2 (9). The latter reaction causes the slow... 

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