Boron compounds, oxidation

The selectivity to alcohol in LPO may be significantly increased when boric acid, meta-hotic acid, or boric anhydride is present in stoichiometric amounts (2). The boron compounds appear to convert alkyUiydroperoxides to alkyl borates and may also intercept alkylperoxy radicals, converting them to alkylperoxyboron compounds these are later converted to alkyl borates. The alkyl borates are resistant to further oxidation they are hydrolyzed to recover alcohols. 

Alkoxides of nonmetals are described in articles about the corresponding compounds (see Boron COMPOUNDS, Boron oxides Silicon compounds). Metal alkyls, in which the alkyl group is bound direcdy to the metal, are also discussed elsewhere (see Aluminum compounds). 

California and in Turkey (see Boron compounds, boron oxides). 

Boron mixed with an oxidizer is used as a pyrotechnic. This ordnance appHcation for missiles and rockets is predominandy military. However, boron is also used in air bags, placed in automobiles as safety devices, for initiating the sodium azide [26628-22-8] which fiHs the bag with nitrogen (13). Other boron compounds are also used in the air-bag pyrotechnic appHcation. 

For the most part boric acid esters are quantitated by hydrolysis in hot water followed by determination of the amount of boron by the mannitol titration (see Boron compounds, boric oxide, boric acid and borates). Separation of and measuring mixtures of borate esters can be difficult. Any water present causes hydrolysis and in mixtures, as a result of transesterification, it is possible to have a number of borate esters present. For some borate esters, such as triethanolamine borate, hydrolysis is sufftciendy slow that quantitation by hydrolysis and titration cannot be done. In these cases, a sodium carbonate fusion is necessary. 

Hydrocarbon Oxidation. The oxidation of hydrocarbons (qv) and hydrocarbon derivatives can be significantly altered by boron compounds. Several large-scale commercial processes, such as the oxidation of cyclohexane to a cyclohexanol—cyclohexanone mixture in nylon manufacture, are based on boron compounds (see Cylcohexanoland cyclohexanone Eibers, polyamide). A number of patents have been issued on the use of borate esters and boroxines in hydrocarbon oxidation reactions, but commercial processes apparently use boric acid as the preferred boron source. The Hterature in this field has been covered through 1967 (47). Since that time the Hterature consists of foreign patents, but no significant appHcations have been reported for borate esters. 

Next to Cr C2, TiC is the principal component for heat and oxidation-resistant cemented carbides. TiC-based boats, containing aluminum nitride, AIN, boron nitride, BN, and titanium boride, TiB2, have been found satisfactory for the evaporation of metals (see Boron compounds, refractory boron compounds Nitrides). 

For a large number of applications involving ceramic materials, electrical conduction behavior is dorninant. In certain oxides, borides (see Boron compounds), nitrides (qv), and carbides (qv), metallic or fast ionic conduction may occur, making these materials useful in thick-film pastes, in fuel cell apphcations (see Fuel cells), or as electrodes for use over a wide temperature range. Superconductivity is also found in special ceramic oxides, and these materials are undergoing intensive research. Other classes of ceramic materials may behave as semiconductors (qv). These materials are used in many specialized apphcations including resistance heating elements and in devices such as rectifiers, photocells, varistors, and thermistors. 

Economic Aspects and Uses. The principal producers in the United States are U.S. Borax and Chemical Corp., North American Chemicals Co., and American Borate Corp. Their combined aimual capacity in 1989 was reported to be 735,000 metric tons of equivalent boron oxide [1303-86-2], B2O2 (20). Of this toimage, 50% is exported. About 30% of boron compounds are used in glass fiber insulation. Another 30% is used in other type fibers and borosihcate glasses. Boron is also used in soaps and detergents, fire retardants, and agriculture (see Boron compounds). 

Oxidative reactions frequently represent a convenient preparative route to synthetic intermediates and end products This chapter includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes and ketones, carboxylic acids, nitrogen compounds, and organophosphorus, -sulfur, -selenium, -iodine, and -boron compounds... 

The main chemical products produced from these minerals are (a) boron oxides, boric acid and borates, (b) esters of boric acid, (c) refractory boron compounds (borides, eu .), (d) boron halides, (e) boranes and carbaboranes and (f) organoboranes. The main industrial and domestic uses of boron compounds in Europe (USA in parentheses) are ... 

Flame resistance A1203, antimony oxides, boron compounds, halogen compounds, phosphate esters, metal hydrates, magnesium compounds, tin compounds, molybdenum compounds, silicones Al, B, Br, Cl, Mo, P, Sb, Si, Sn, Zn... 

This section will focus on homonuclear neutral or anionic clusters of the elements aluminum, gallium, indium, and thallium, which have an equal number of cluster atoms and substituents. Thus, they may clearly be distinguished from the metalloid clusters described below, which in some cases have structures closely related to the allotropes of the elements and in which the number of the cluster atoms exceeds the number of substituents. The compounds described here possess only a single non-centered shell of metal atoms. With few exceptions, their structures resemble those of the well-known deltahedral boron compounds such as B4(CMe3)4 [30], B9CI9 [31] or [B H ]2 [32]. The oxidation numbers of the elements in these... 

---