Orthoboric acid, 132

The element is not found free in nature, but occurs as orthoboric acid usually found in certain volcanic spring waters and as borates in boron and colemantie. Ulexite, another boron mineral, is interesting as it is nature s own version of "fiber optics."... 

H3B03 orthoboric acid (or boric acid) H4P2O3 peroxodiphosphoric acid... 

Although all four tocopherols have been synthesized as their all-rac forms, the commercially significant form of tocopherol is i7//-n7i a-tocopheryl acetate. The commercial processes ia use are based on the work reported by several groups ia 1938 (15—17). These processes utilize a Friedel-Crafts-type condensation of 2,3,5-trimethylhydroquinone with either phytol (16), a phytyl haUde (7,16,17), or phytadiene (7). The principal synthesis (Fig. 3) ia current commercial use iavolves condensation of 2,3,5-trimethylhydroquiQone (13) with synthetic isophytol (14) ia an iaert solvent, such as benzene or hexane, with an acid catalyst, such as ziac chloride, boron trifluoride, or orthoboric acid/oxaUc acid (7,8,18) to give the all-rac-acetate ester (15b) by reaction with acetic anhydride. Purification of tocopheryl acetate is readily accompHshed by high vacuum molecular distillation and rectification (<1 mm Hg) to achieve the required USP standard. 

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. 

Forms of Boric Acid. Orthoboric acid, B(OH)3, formula wt, 61.83, crystaUi2es from aqueous solutions as white, waxy plates that are triclinic ia nature sp gi 4, 1.5172. Its normal melting poiat is 170.9°C, however, when heated slowly it loses water to form metaboric acid, HBO2, formula wt, 43.82, which may exist ia one of three crystal modifications. Orthorhombic HBO2-III or a-form d = 1.784 g/mL, mp = 176° C) forms first around 130°C and gradually changes to monoclinic HBO2-II or P-form (d = 2.045 g/mL, mp = 200.9° C). Water-vapor pressures associated with these decompositions foUow. To convert kPa to mm Hg, multiply by 7.5. 

Chemical Designations - Synonyms Boracic Acid Orthoboric Acid Chemical Formula H3BO3. Observable Characteristics - Physical State (as normally shipped) Solid Color White Odor. None. Physical and Chemical Properties - Physical State at 15 and 1 atm. Solid Molecular Weight 61.83 Boiling Point at 1 atm. Not pertinent (decomposes) Freezing Point Not pertinent Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 1.51 at I4°C (solid) Vapor (Gas) Density Not pertinent Ratio of Specific Heats of Vapor (Gas) Not pertinent Heat... 

Orthoboric acid, B(OH)3, is the normal end product of hydrolysis of most boron compounds and is usually made ( 160 000 tonnes pa) by acidification of aqueous solutions of borax. Price depends on quality, being 805 per tonne for technical grade and about twice that for refined material (1990). It forms flaky, white, transparent crystals in which a planar array of BO3 units is joined by unsymmetrical H bonds as shown in Fig. 6.25. In contrast to the short O—H O distance of 272 pm within the plane, the distance between consecutive layers in the ciystal is 318 pm, thus accounting for the pronounced basal cleavage of the waxy, plate-like ciystals, and their low density (1.48 g cm ). B(OH)3 is a very weak monobasic acid and acts exclusively by hydroxyl-ion acceptance rather than proton donation ... 

Orthoarsenic acid, 3 264—265 Orthoboric acid, 4 242t, 249—255 Orthoclase, hardness in various scales, l 3t Orthocortex, in wool fibers, 11 173 Orthodontics, superelastic and pseudoelastic SMA devices in, 22 350-351 Orthoesters, 10 498 Orthoferrites, 11 56t, 57 Orthogonal matrices, 6 27 ort/io-hydrogen, 13 759, 760—761 Orthokinetic flocculation, 11 631 22 56 Orthokinetic flocculator, 22 59 Orthomyxoviruses, 3 136—137... 

Occurrence. It is found as borates or as orthoboric acid in some volcanic spring waters. Important sources are borax (Na2B407 10H2O), kemite (Na2B407 4H20), colemanite (Ca2B60n 5H20). 

Most of the problems of side reactions can be circumvented by using a mixture of unhydrous sulfuric acid (containing no free SO3, a powerful oxidant) and orthoboric acid [4,8], The superacidic nature of this sulfonation mixture ensures complete protonation and the lack of free SO3 excludes the possibility of oxidation. In addition, the number and position of the sulfonate groups can be more effectively controlled than by using oleum for... 

Consider planar molecules, such as 1,2-dichlorobenzene (C2v), glyoxal (Fig. 1, structure 6 point group C2A), orthoboric acid [B(OH)3 structure 7 point group C3h), naphthalene (D2h), or benzene (D6h). Such a molecule will have all its atoms in one principal axes plane, say the yz plane, so that x, = 0 for all i. 

The most versatile of all borates as a synthetic reagent, orthoboric acid, B(0H)3, is the second most important refined borate product in terms of industrial tonnage. It is typically manufactured by reacting a borate ore, particularly kernite or colemanite, with sulfuric acid, Eqs. (8) and (9). 

Orthoboric acid H3803 or B203.3H20 Metaboric acid HBOz or B2O3.H20 Tetraboric acid H2B407 or 2B203.H20... 

Organic coordination groups, nomenclature of, 2 267 Organogermanium compounds, 5 64 nomenclature of, 5 64 Organosilazane compounds, 5 55, 62 Organosilicon compounds, 3 50 nomenclature of, 2 266 3 55 Orthite, extraction of, 2 44 Orthoboric acid, esters of, 6 29 Orthoperiodic acid (HsICh), 1 172, 173... 

Synonyms Boracic acid, Hydrogen borate, Orthoboric acid. 

Boric acid or orthoboric acid (commercially known as Optibor ) is a white triclinic crystal that is soluble in water (5.46 wt.%), alcohols, and glycerin. It is a weak acid and has a pH of 4 (saturated solution at room temperature). Upon heating in air to above 75°C, it loses part of its water of hydration to form metaboric acid (HBO at around 120°C-130°C. The metaboric acid can be further dehydrated to boric oxide at around 260°C-270°C. 

In this preparation, borax, the sodium salt of tetraboric acid, is chosen as the source of boron. Although boron is decidedly a non-metal, still its acid-forming characteristics are not highly developed and its acids are readily displaced by strong acids from solutions of their salts. Thus tetraboric acid, H2B4O7, would be set free from borax by hydrochloric acid, but the acid which actually crystallizes is the more highly hydrated orthoboric acid, H3BO3. 

Explain the relations between orthoboric acid, metaboric acid, tetraboric acid, and boric anhydride. Experiment Place a few grams of boric acid on a watch glass upon the steam table (100-110°) and leave for hour. What is formed What would be formed if the acid were heated to 140° Suspend a little of the acid in a loop of platinum wire, and heat in the Bunsen flame. What is formed ... 

Repeat if necessary the last part of Experiment 1, noticing the color imparted to the flame while the orthoboric acid is first melting, and again when a clear bead of boric anhydride is obtained. 

Starting materials for the direct synthesis of (Si,B)-ZSM-5 were fumed silica (Cabosil), tetrapropylammonium bromide (TPA-Br), ammonium fluoride and orthoboric acid (16). The source of silica was mixed with TPA-Br and water and then a mixed solution of NH4F and H3BO3 was added under vigorous stirring. The resultant gel was homogenized for 1.5 h and transferred into a Teflon-lined stainless steel autoclave which was then heated at 200°C for 17 days. Zeolite crystals were washed, dried at 60°C and hydrated in a desiccator. 

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