Boric acid, oxidation with

Boron III) oxide, B2O3, is obtained by ignition of boric acid. Combines with water to reform B(0H)3. The fused oxide dissolves metal oxides to give borates. 

From Boric Oxide and Alcohol. To avoid removing water, boric oxide, B2O3, can be used in place of boric acid. The water of reaction (eq. 4) is consumed by the oxide (eq. 5). Because boric acid reacts with borates at high temperatures, it is necessary to filter the reaction mixture prior to distillation of the product. Only 50% of the boron can be converted to ester by this method. In cases where this loss can be tolerated, the boric oxide method is convenient. This is particularly tme for methyl borate and ethyl borate preparation because formation of the undesirable azeotrope is avoided. 

Curves which are of the same form as curve B have been obtained for the diazo-coupling (52) and iodination (, 7,13) of 8-hydroxyquinoline-5-sulfonic acid and its metal complexes and for the oxidation of glucose and its boric acid complex with ferricyanide (50). 

Complex tungstic acids arc numerous mid interesting. I hosplnirir, arsenic, antimonic, vanadic, and boric, acids condense with varying aiunuuis of tungstic acid. The ratio of the, otlner oxide, to W(), varies from 1 7 in 1 24 or more-... 

CHEMICAL PROPERTIES flammable liquid thermally unstable corrosive to natural rubber hydrolyzes slowly with heat in water to form boric acid reacts with ammonia to form a diammoniate reacts vigorously with strong oxidizers decomposes very slowly at 150°C (302°F) FP (30°C, 86 F) LFL/UFL (0.42%, 98%) AT (35°C, 95 F) HF (42.7 kJ/mol liquid at 25°C). 

A number of low-activity catalysts that could control oxidation to some extent were eventually identified. These were metal oxides from Groups V and VI, such as vanadium, molybdenum, and tungsten, particulariy when mixed with phosphoric, arsenic, or boric acids. Oxidation was controlled by choosing the appropriate temperature and contact time. At first it was difficult to achieve reasonable selectivity when dealing with exothermic reactions. 

Prepared by condensing p-chlorophenol with phlhalic anhydride in sulphuric acid solution in the presence of boric acid. The chlorine atom is replaced by hydroxyl during the condensation. It can also be prepared by oxidation of anthraquinone or 1-hydroxyanthraquinone by means of sulphuric acid in the presence of mercury(ll) sulphate and boric acid. 

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. 

Manufacture. Fluoroborate salts are prepared commercially by several different combinations of boric acid and 70% hydrofluoric acid with oxides, hydroxides, carbonates, bicarbonates, fluorides, and bifluorides. Fluoroborate salts are substantially less corrosive than fluoroboric acid but the possible presence of HF or free fluorides cannot be overlooked. Glass vessels and equipment should not be used. 

Cyclohexane. The LPO of cyclohexane [110-82-7] suppUes much of the raw materials needed for nylon-6 and nylon-6,6 production. Cyclohexanol (A) and cyclohexanone (K) maybe produced selectively by using alow conversion process with multiple stages (228—232). The reasons for low conversion and multiple stages (an approach to plug-flow operation) are apparent from Eigure 2. Several catalysts have been reported. The selectivity to A as well as the overall process efficiency can be improved by using boric acid (2,232,233). K/A mixtures are usually oxidized by nitric acid in a second step to adipic acid (233) (see Cyclohexanol and cyclohexanone). 

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). 

Lead borate moaohydrate [14720-53-7] (lead metaborate), Pb(B02)2 H20, mol wt 310.82, d = 5.6g/cm (anhydrous) is a white crystalline powder. The metaborate loses water of crystallization at 160°C and melts at 500°C. It is iasoluble ia water and alkaHes, but readily soluble ia nitric and hot acetic acid. Lead metaborate may be produced by a fusion of boric acid with lead carbonate or litharge. It also may be formed as a precipitate when a concentrated solution of lead nitrate is mixed with an excess of borax. The oxides of lead and boron are miscible and form clear lead-borate glasses in the range of 21 to 73 mol % PbO. 

Various other soft materials without the layer—lattice stmcture are used as soHd lubricants (58), eg, basic white lead or lead carbonate [598-63-0] used in thread compounds, lime [1305-78-8] as a carrier in wire drawing, talc [14807-96-6] and bentonite [1302-78-9] as fillers for grease for cable pulling, and zinc oxide [1314-13-2] in high load capacity greases. Graphite fluoride is effective as a thin-film lubricant up to 400°C and is especially useful with a suitable binder such as polyimide varnish (59). Boric acid has been shown to have promise as a self-replenishing soHd composite (60). 

Phosphoric acid, aside from its acidic behavior, is relatively unreactive at room temperature. It is sometimes substituted for sulfuric acid because of its lack of oxidising properties (see SuLFURic ACID AND SULFURTRIOXIDe). The reduction of phosphoric acid by strong reducing agents, eg, H2 or C, does not occur to any measurable degree below 350—400°C. At higher temperatures, the acid reacts with most metals and their oxides. Phosphoric acid is stronger than acetic, oxaUc, siUcic, and boric acids, but weaker than sulfuric, nitric, hydrochloric, and chromic acids. 

Monobasic aluminum acetate is dispensed as a 7% aqueous solution for the topical treatment of certain dermatological conditions, where a combination of detergent, antiseptic, astringent, and heat-dispersant effects are needed (12). The solution, diluted with 20—40 parts water, is appHed topically to the skin and mucous membranes as a wet dressing (13). Burrow s solution, prepared from aluminum subacetate solution by the addition of a specific amount of acetic acid, is also used as a topical wet dressing. Standards of purity and concentration have been estabHshed for both pharmaceutical aluminum acetate solutions (13). Each 100 mL of aluminum subacetate solution yields 2.30—2.60 g of aluminum oxide and 5.43—6.13 g of acetic acid upon hydrolysis. For the Burow s solution, each 100 mL yields 1.20—1.45 g of aluminum oxide and 4.25—5.12 g of acetic acid. Both solutions may be stabilized to hydrolysis by the addition of boric acid in amounts not to exceed 0.9% and 0.6% for the subacetate and Burow s solutions, respectively (13). 

Lower Oxides. A number of hard, refractory suboxides have been prepared either as by-products of elemental boron production (1) or by the reaction of boron and boric acid at high temperatures and pressures (39). It appears that the various oxides represented as B O, B O, B22O2, and B23O2 may all be the same material ia varying degrees of purity. A representative crystalline substance was determined to be rhombohedral boron suboxide, B12O2, usually mixed with traces of boron or B2O3 (39). A study has been made of the mechanical properties of this material, which exhibits a hardness... 

The name boric acid is usually associated with orthoboric acid, which is the only commercially important form of boric acid and is found ia nature as the mineral sassoflte. Three crystalline modifications of metaboric acid also exist. AH these forms of boric acid can be regarded as hydrates of boric oxide and formulated as B2O3 3H20 for orthoboric acid and B2O3 H20 for metaboric acid. 

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... 

Anhydrous metal borates may be prepared by heating the hydrated salts to 300—500°C, or by direct fusion of the metal oxide with boric acid or B2O2. Many binary and tertiary anhydrous systems containing B2O2 form vitreous phases over certain ranges of composition (145). 

Preparation. Boron carbide is most commonly produced by the reduction of boric oxide with carbon in an electric furnace between 1400 and 2300°C. In the presence of carbon, magnesium reduces boric oxide to boron carbide at 1400—1800°C. The reaction is best carried out in a hydrogen atmosphere in a carbon tube furnace. By-product magnesium compounds are removed by acid treatment. 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

It is prepared by pasting potassium or sodium dichromate with three times its weight of boric acid, roasting the mixture at 500°C in a muffle furnace in an oxidizing atmosphere, then hydrolyzing the melt with water and superheated steam. The product is then dried and ground. 

The oxidation of cyclohexane to a mixture of cyclohexanol and cyclohexanone, known as KA-od (ketone—alcohol, cyclohexanone—cyclohexanol cmde mixture), is used for most production (1). The earlier technology that used an oxidation catalyst such as cobalt naphthenate at 180—250°C at low conversions (2) has been improved. Cyclohexanol can be obtained through a boric acid-catalyzed cyclohexane oxidation at 140—180°C with up to 10% conversion (3). Unreacted cyclohexane is recycled and the product mixture is separated by vacuum distillation. The hydrogenation of phenol to a mixture of cyclohexanol and cyclohexanone is usually carried out at elevated temperatures and pressure ia either the Hquid (4) or ia the vapor phase (5) catalyzed by nickel. 

Alkylamines react with leucoquinizarin in a stepwise manner to give l-alh anaino-4-hydroxyanthraquinone, and 1,4-diaLkylamino derivatives after air oxidation. Aromatic amines react similarly in the presence of boric acid as a catalyst. The complex formed (129) causes the less nucleophilic aromatic amines to attack at the 1-, and 4-positions. 

Cl Acid Violet 43 [4430-18-6] (2) (Cl 60730) is one of the first acid dyes, invented in 1894. This dye exhibits good leveling and is available from leiicoquinizarin by reaction with -toluidine in the presence of boric acid, followed by oxidation and subsequent sulfonation (133). 

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