Boron oxides and oxoacids

Boron (like silicon) invariably occurs in nature as 0X0 compounds and is never found as the element or even directly bonded to any other element than oxygen. The structural chemistry of B-O compounds is characterized by an extraordinary complexity and diversity which rivals those of the borides (p. 145) and boranes (p. 151). In addition, vast numbers of predominantly organic compounds containing B-O are known. 

Supplement to Mellor s Comprehensive Treatise on Inorganic and Theoretical Chemistry , Vol. V, Boron Part A, Boron-Oxygen Compounds , Longman, London, 1980, 825 pp. See also J. R. Bowser and T. P. Fehlner, Chap. 1 in H. W. Roesky (ed.). Rings, Clusters and Polymers of Main Group and Transition Elements, Elsevier, Amsterdam, 1989, pp. 1-48. 

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  

Layer structure of B(OH)3. Interatomic distances are B-O 136pm. O-H 97pm, O—H---0 272pm. Angles at B are 120° and at O 126° and 114°. The H bond is almost linear. 

Its acidity is considerably enhanced by chelation with polyhydric alcohols (e.g. glycerol, mannitol) and this forms the basis of its use in analytical chemistry e.g. with mannitol p T drops to 5.15, 

7 Trivial exceptions to this sweeping generalization are NaBp4 (femicite) and (K,Cs)Bp4 (avogadrite) which have been reported from Mt. Vesuvius, Italy. 

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Reactivity and Incompatibility DMSO reacts violently with strong oxidizers, many acyl halides, boron hydrides, and alkali metals. DMSO can form explosive mixtures with metal salts of oxoacids (sodium perchlorate, iron(III) nitrate). 

SULFICYLBIS (METHANE) (67-68-5) CjHjOS (CH3)2S0 Combustible liquid [explosion limits in air (vol %) 2.6 to 63.0 flashpoint 203°F/95°C oc autoignition temp 419°F/215°C Fire Rating 2]. Violent or explosive reaction with strong oxidizers, acryl halides, aryl halides and related compounds, alkali metals p-bromobenzoyl acetanilide, boron compounds, especially hydrides iodine pentafluoride, magnesium perchlorate, methyl bromide, perchloric acid, periodic acid, silver fluoride, sodium hydride, potassium permanganate. Forms powerfully explosive mixtures with metal salts of oxoacids [iron(III)nitrate, phosphonic acid, sodium perchlorate]. On small fires, use dry chemicals or COj extinguishers. 

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