Boric acid reactions

This question is essentially a mechanistic one in which the two candidates reaction with the diol mechanism are in rapid equilibrium with each other. Such mechanistic questions can be more properly answered by studying the kinetics of the reaction. A kinetic study of the reaction boric acid and tartaric acid has been reported (17). It was found that tartaric acid reacts with boric acid and not the borate ion. Also, the relaxation time for this reaction is near 20 msec. 

In the past, boric acid was falsely considered to be relatively non-toxic, and had an unwarranted reputation as a germicide. However, it is only bacteriostatic, even in a saturated aqueous solution, and can cause adverse reactions. Boric acid has often proved poisonous, either by ingestion or after local use. Cases from the world literature have been reviewed (1,2). In 172 cases of boric acid intoxication, including 83 deaths, 37 deaths occurred after external use, including 23 children with nappy rash. From 1974 to 1984, the Poison Centre in Paris recorded 134 cases of intoxication with boric acid or borates, 88 of which were accidental and 31 iatrogenic. 

Color reactions Boric acid (hydroxyquinones). Dimethylaminobenzaldehyde (pyrroles). Ferric chloride (enols, phenols). Haloform test. Phenylhydrazine (Porter-Silber reaction). Sulfoacetic acid (Liebermann-Burchard test). Tetranitromethane (unsaturation). Condensation catalysts /3-Alanine. Ammonium acetate (formate). Ammonium nitrate. Benzyltrimethylammonium chloride. Boric acid. Boron trilluoride. Calcium hydride. Cesium fluoride. Glycine. Ion-exchange resins. Lead oxide. Lithium amide. Mercuric cyanide. 3-Methyl-l-ethyl-2-phosphoiene-l-oxlde. 3-Methyl-1-phenyi-3-phoipholene-1-oxide. Oxalic acid. Perchloric acid. Piperidine. Potaiaium r-butoxIde. Potassium fluoride. Potassium... 

In this Lewis acid-base reaction, boric acid accepts a pair of electrons from the hydroxide ion that is derived from the H2O molecule. 

Initially, BN was synthesized by the pyrolysis of boric acid and urea in the presence of ammonia [27]. In this reaction, boric acid presumably reacts with urea to form a urea-boric acid complex gel, which on pyrolysis in an ammonia atmosphere results in the formation of BN [28]. Precursors for BN recently received the greatest attention, with emphasis on borazine-derived polymers. It has been recognized that borazine (1) can form polymeric chains of B and N, which can form BN ceramics on thermal pyrolysis [29]. The polymerization gives a graphitelike hexagonal layered structure (2) ... 

In the presence of glycerol or mannitol (polyhydroxo compounds) boric acid behaves as a much stronger acid the reaction can be represented as ... 

Alkyl borates. By heating boric acid with excess of the alcohol the water formed in the reaction is removed by fractional distillation as an azeo tropic mixture with the alcohoi, for example ... 

This reaction is due to the combination of two da hydroxyl groups of the compound with the boric acid to form a much stronger monobasic acid ... 

Another type of demasking involves formation of new complexes or other compounds that are more stable than the masked species. For example, boric acid is used to demask fluoride complexes of tin(IV) and molybdenum(VI). Formaldehyde is often used to remove the masking action of cyanide ions by converting the masking agent to a nonreacting species through the reaction ... 

Boron trifluoride [7637-07-2] (trifluoroborane), BF, was first reported in 1809 by Gay-Lussac and Thenard (1) who prepared it by the reaction of boric acid and fluorspar at duU red heat. It is a colorless gas when dry, but fumes in the presence of moisture yielding a dense white smoke of irritating, pungent odor. It is widely used as an acid catalyst (2) for many types of organic reactions, especially for the production of polymer and petroleum (qv) products. The gas was first produced commercially in 1936 by the Harshaw Chemical Co. (see also Boron COMPOUNDS). 

The hydrolysis of BF occurs stepwise to BF OH, BF2 (OH)2, and BF(OH)3. By conductivity measurements the reaction of boric acid and HF was found to form H[BF2(OH)] [15433-40-6] rapidly subsequentiy HBF formed much more slowly from HBF OH. These studies demonstrate that BF is... 

Manufacture, Shipping, and Waste Treatment. Fluoroboric acid (48%) is made commercially by direct reaction of 70% hydroduoric acid and boric acid, H BO (see Boron compounds). The reaction is exothermic and must be controlled by cooling. 

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. 

Formaldehyde is readily reduced to methanol by hydrogen over many metal and metal oxide catalysts. It is oxidized to formic acid or carbon dioxide and water. The Cannizzaro reaction gives formic acid and methanol. Similarly, a vapor-phase Tischenko reaction is catalyzed by copper (34) and boric acid (38) to produce methyl formate ... 

Reactions. The most important commercial reaction of cyclohexane is its oxidation (ia Hquid phase) with air ia the presence of soluble cobalt catalyst or boric acid to produce cyclohexanol and cyclohexanone (see Hydrocarbon oxidation Cyclohexanoland cyclohexanone). Cyclohexanol is dehydrogenated with 2iac or copper catalysts to cyclohexanone which is used to manufacture caprolactam (qv). 

Lithium Borates. Lithium metaborate [13453-69-5], LLBO2 2H20, is prepared from reaction of lithium hydroxide and boric acid. It is used as the fluxing agent for the matrix for x-ray fluorescence analytical techniques and in specialty glasses and enamels. The anhydrous salt melts at 847°C. 

Petoxycatboxyhc acids also have been prepared by the reaction of acid chlorides, anhydrides, or boric-catboxyhc anhydrides with hydrogen or sodium peroxide. These reactions ate carried out at low temperature and with excess peroxide to avoid the formation of diacyl peroxides (44,168,181,184). 

The tertiary metal phosphates are of the general formula MPO where M is B, Al, Ga, Fe, Mn, etc. The metal—oxygen bonds of these materials have considerable covalent character. The anhydrous salts are continuous three-dimensional networks analogous to the various polymorphic forms of siHca. Of limited commercial interest are the alurninum, boron, and iron phosphates. Boron phosphate [13308-51 -5] BPO, is produced by heating the reaction product of boric acid and phosphoric acid or by a dding H BO to H PO at room temperature, foUowed by crystallization from a solution containing >48% P205- Boron phosphate has limited use as a catalyst support, in ceramics, and in refractories. 

Properties and Reactions. Several methods of preparation are available for POCI3, including partial hydrolysis of PCl by heating in the presence of oxaflc or boric acid, chlorination and hydrolysis of PCl in the presence of H PO, ... 

In this process, catalysts, such as boric acid, molybdenum oxide, zirconium, and titanium tetrachloride or ammonium molybdate, are used to accelerate the reaction. The synthesis is either carried out in a solvent (aUphatic hydrocarbon, trichlorobenzene, quinoline, pyridine, glycols, or alcohols) at approximately 200°C or without a solvent at 300°C (51,52). 

A continuous process has been described (14) which can produce either the amide or the nitrile by adjusting the reaction conditions. Boric acid has been used as a catalyst in the amidation of fatty acid (15). Other catalysts employed include alumina (16), titanium, and 2inc alkoxides (17). The difficulty of complete reaction during synthesis has been explained by the formation of RCOOH NH RCOO , a stable intermediate acid ammonium salt (18). 

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). 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

Inorganic Esters. Boric acid and borax form cycHc esters with poly(vinyl alcohol) (85—100). The reaction is markedly sensitive to pH, boric acid concentration, and the cation-to-boron ratio. An insoluble gel is formed at pH above 4.5—5.0 ... 

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