Pentaborane

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for particulate matter containing no asbestos and 1% crystalline silica is 3mg/m for respirable size fraction and lOmg/m for inhalable mass fraction. Exposure to any substance in the particulate mass that has a designated TLV should be controlled to that value. 

Dockery DW, et al An association between air pollution and mortality in six U.S. cities. N Engl JMed 329 1753, 1993 

Pope CA, et al Particulate air pollution as a predictor of mortality in a prospective study of U.S. adults. Am J Respir Crit Care Med 151 669, 1995 

Pope CA, et al Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA 287(9) 1132-1141,2002 

Krewski D, et al Reanalysis of the Harvard Six Cities study and the American Cancer Society Study of Particulate Air Pollution and Mortality A Special Report of the Institute s Particle Epidemiology Reanalysis Project. Cambridge, AlA Health Effects Institute, 2000 

Submitted by V. R. MILLER and G. E. RYSCHKEWITSCH Checked by D. F. GAINESt and N. KEIPEt 

The diborane and the contents of the vacuum-line trap may be diluted with nitrogen and vented into a solution of pyridine in benzene for disposal. (Alternatively pyridine may be condensed in the vacuum-line trap.) Pentaborane(9) is very soluble in the greases normally used as stopcock lubricants. Care must be taken to remove it by evacuation from exposed joints before they are exposed to air. 

It must be emphasized that any apparatus that has been degreased with trichloroethylene, or any other of the above-mentioned compounds, should be carefully dried to remove the solvent before exposure to pentaborane(9). 

Pure pentaborane(9) in dry glass ampuls may be stored for long periods at room temperature. The presence of impurities will result in the generation of pressure by formation of lower boranes and hydrogen. 

Pentaborane(9) boils at 58° and freezes at 47°. The vapor pressure of the liquid is represented by the equation 

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Other boron hydrides are known, most of them having the general formula B H + 4- for example pentaborane, B5H9, decaborane, BjqHi4. Each can be made by heating diborane in suitable conditions for example at 420 K, decaborane is obtained. Boron hydrides have been tried as rocket fuels. 

When a boron atom of a borane is replaced by a heteroelement, the compounds are called carbaboranes, phosphaboranes, thiaboranes, a2aboranes, etc, by an adaptation of organic replacement nomenclature. The numbering of the skeleton in heteroboranes is such that the heteroelement is given the lowest possible number consistent with the conventions of the parent borane. Thus C2B2H is dicarba- /(9j (9-pentaborane(5) and could occur as the 1,2-, 2,3-, or 1,5-isomeric forms (l,2-dicarba- /(9j (9-pentaborane(5) [23777-70-0] 2,3-dicarba- /(9j (9-pentaborane(5) [30396-61-3] and... 

The valence theory (4) includes both types of three-center bonds shown as well as normal two-center, B—B and B—H, bonds. For example, one resonance stmcture of pentaborane(9) is given in projection in Figure 6. An octet of electrons about each boron atom is attained only if three-center bonds are used in addition to two-center bonds. In many cases involving boron hydrides the valence stmcture can be deduced. First, the total number of orbitals and valence electrons available for bonding are determined. Next, the B—H and B—H—B bonds are accounted for. Finally, the remaining orbitals and valence electrons are used in framework bonding. Alternative placements of hydrogen atoms require different valence stmctures. 

Penta.bora.ne(9), Pentaborane(9) and can be prepared by gas-phase pyrolysis of B2H under different conditions. Pentaborane(9) is a... 

Polyhedral Boron Hydrides. Although relatively large quantities of polyhedral boron hydrides and carboranes have been produced under various government contracts, these materials are not currendy produced on a regular commercial basis. Pentaborane(9) nido- and decaborane(14) and carboranes, such as the ortho and meta-carboranes closo-1 1 well as various other derivatives, are... 

PELARGONYL PEROXIDE see DI-N-HONANOYL PEROXIDE PENICILLIN see BENZYLPENICILLIN PENTABORANE... 

Penta Manufacturmg Company, 242 Pentaborane, 102 Pentachloronitrobenzene, 102 Pentachlorophenol, 103 Pentaerythritol, 103... 

Smiciuresof (he three iwineisof The 1,1 iiomci compri es two pentaborane(9) groups linked ineclip >eiJ... 

Boranes are usually named by indicating the number of B atoms with a latin prefix and the number of H atoms by an arabic number in parentheses, e.g. B5H9, pentaborane(9) B5H11, pentaboranefl 1). Names for anions end in ate rather than ane and specify both the number of H and B atoms and the charge, e.g. BsHs" octahydropentaboratefl—). Further information can be provided by the optional inclusion of the italicized descriptors closo-, nido-, arachno-, hypho- and conjuncto-, e.g. ... 

Pentaborane. See Vol 2, B254-L to B256-R Addnl Ref Anon, Toxic and Hazardous Industrial Chemicals Safety Manual , The International Technical Information Institute, Tokyo (1975), 396-7... 

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