Boron and Its Compounds

PURPOSE OF EXPERIMENT Study some properties and reactions of boron and some boron compounds, and analyze a mixture containing borax. 

Orthoboric acid forms white, needle-like crystals in which B(0H)3 units are linked together by hydrogen bonds to form infinite sheets. The ortho prefix indicates that this particular oxyacid of B(III) is formally the most fully hydrated one. This nomenclature also carries over to oxyacids of other nonmetals such as silicon, phosphorus, and sulfur. 

To each of three different 13 x lOO-mm test tubes, add 2 mL of distilled water and 2 drops of bromocresol green indicator (color change from pH 3.8 to 5.4). Add 1 drop of 6 H aqueous ammonia, NH3, solution to the first test tube and 1 drop of 3 M hydrochloric acid, HCl, solution to the third test tube. The first and third test tubes will then serve as reference colors for the indicator. 

Add a couple dozen crystals of orthoboric acid, H3BO3, to the second test ttibe, and dissolve the crystals with stirring. Describe what you observe in TABLE 35.lA. 

Solutions of H3BO3 are acidic because the concentration of OH has been reduced, not because the concentration of H+ has been increased by dissociation from H3BO3. Thus, H3BO3 acts not as a Br nsted-Lowry acid (proton donor), but as a Lewis acid (lone pair acceptor, from OH ), as illustrated by the following equation. 

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Muetterties, E. F., Ed. (1967). The Chemistry of Boron and Its Compounds. Wiley, New York. A collection of chapters on different topics in boron chemistry. 

Turkey reports investigating applications of Boron compounds. To this end, Turkey is establishing the Boron Institute, which will investigate new application areas for boron and its compounds. 

International Symposium on the Health Effects of Boron and its Compounds. Irvine, California. September 16-17, 1992. (Proceedings.) Environ. Health Perspect. 1994, 102 (Suppl. 7), 1-141. 

Toxicosis in animals has resulted from ingestion of boric acid or borax solutions, from topical applications of boric acid solutions to damaged skin, and from inhalation of boranes the exact mechanisms of action are not understood. Boron and its compounds are potent teratogens when applied directly to the embryo, bnt there is no evidence of mutagenicity or carcinogenicity. Boron s unique affinity for cancerons tissnes has been exploited in neutron capture radiation therapy of malignant hnman brain tnmors. 

Mastromatteo, E. and E. Sullivan. 1994. Summary international symposium on the health effects of boron and its compounds. Environ. Health Perspec. 102(Suppl. 7) 139-141. 

Gmelin Handbook Volumes on Boron and its Compounds (a) Main Volume (1926) (b) Supplement vol. 1 (1954) (c) Compounds 8 (NSSV 33), The tetrahydroborate ion and its derivatives (1976) (d) Compounds 9 (NSSV 34), Boron-halogen compounds , Part 1 (1976) (e) Compounds 10 (NSSV 37), Boron compounds with coordination number 4 (1976) (f) Compounds 15 (NSSV 46), Amine-boranes (1977) (g) Compounds 19 (NSSV 53), Boron-halogen compounds , Part 2 (1978) (h) Supplement Volumes (1980-82), Springer-Verlag, Berlin. 

G. Urry, Boron Halides, in The Chemistry of Boron and Its Compounds, E. L. Muetterties (ed.), John Wiley Sons, Inc., New York, 1967. 

W. Gerrard, The Chemistry of Boron, Academic Press, New York, 1961 E. L. Muetterties, The Chemistry of Boron and its Compounds, John Wiley, New York, 1967 A. N. Nesmeyanov, R. A. Sokolik, Methods of Elemento-organic Chemistry, North-Holland, Amsterdam, 1967, Vol. 1 R. Kdster, Houben-Weyl Methoden der Organischen Chemie, Georg Thieme Verlag, Stuttgart, 1984 D. S. Matteson, in The Chemistry of the Metal-Carhon Bond (Eds. F. Hartley, S. Patai), John Wiley, New York, 1987, Vol. 4, pp. 307-409 ref. [2]. 

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