Carbon boron oxides

Nitric oxide Aluminum, BaO, boron, carbon disulflde, chromium, many chlorinated hydrocarbons, fluorine, hydrocarbons, ozone, phosphine, phosphorus, hydrazine, acetic anhydride, ammonia, chloroform, Fe, K, Mg, Mn, Na, sulfur... 

Unlike boron, aluminum, gallium, and indium, thallium exists in both stable univalent (thaHous) and trivalent (thaUic) forms. There are numerous thaHous compounds, which are usually more stable than the corresponding thaUic compounds. The thaUium(I) ion resembles the alkaU metal ions and the silver ion in properties. In this respect, it forms a soluble, strongly basic hydroxide and a soluble carbonate, oxide, and cyanide like the alkaU metal ions. However, like the silver ion, it forms a very soluble fluoride, but the other haUdes are insoluble. Thallium (ITT) ion resembles aluminum, gallium, and indium ions in properties. 

Another useful reagent for introduction of the carbonyl carbon is dichloromethyl methyl ether. In the presence of a hindered alkoxide base, it is deprotonated and acts as a nucleophile toward boron. Rearrangement then ensues with migration of two boron substituents. Oxidation gives a ketone. 

Compounds containing carbon in a negative oxidation state are properly called carbides, and many such compounds are known. In a manner analogous to the behavior of hydrogen and boron, carbon forms three types of binary compounds, which are usually called ionic, covalent, and interstitial... 

As shown in Table 10.5, non-metaUic fuels used as ingredients of pyrolants are boron, carbon, silicon, phosphorus, and sulfur. Similarly to metal particles, non-metal particles are oxidized at their surfaces. The processes of diffusion of oxidizer fragments to the surface of a particle and the removal of oxidized fragments therefrom are the rate-controlling steps for combustion. 

Hydroboration of hex-1 -yne, for example, gives the vinylborane with boron on the less highly substituted carbon. Oxidation of this intermediate gives an enol that quickly tautomerizes to hexanal. 

Most borides are chemically inert in bulk form, which has led to industrial applications as engineering materials, principally at high temperature. The transition metal borides display a considerable resistance to oxidation in air. A few examples of applications are given here. Titanium and zirconium diborides, alone or in admixture with chromium diboride, can endure temperatures of 1500 to 1700 K without extensive attack. In this case, a surface layer of the parent oxides is formed at a relatively low temperature, which prevents further oxidation up to temperatures where the volatility of boron oxide becomes appreciable. In other cases the oxidation is retarded by the formation of some other type of protective layer, for instance, a chromium borate. This behavior is favorable and in contrast to that of the refractory carbides and nitrides, which form gaseous products (carbon oxides and nitrogen) in air at high temperatures. Boron carbide is less resistant to oxidation than the metallic borides. 

Many normal oxides are formed on burning the element in air or oxygen. This is true not only of the non-metals boron, carbon, sulphur and phosphorus, but also for the volatile zinc, cadmium, indium and thallium, the transition metals cobalt and iron, in finely divided condition, and the noble metals osmium, ruthenium and rhodium. With some elements, limiting the supply of oxygen produces the lower oxide (e,g, P40g in place of P4O40 (p. 332)). 

Hydroboration of alkynylsilanes with dicyclohexylborane proceeds in a stereo-and regioselective manner, placing the boron at the silicon-bearing carbon. Oxidation of the resultant alkenylborane with excess alkaline hydrogen peroxide produces, via an acyl silane intermediate (see Section 7.9), the carboxylic acids in greater than 80% yields. The alkynylsilanes may be generated in situ as illustrated by the one-pot transformation below. 

In the industrial manufacture of boron carbides, boron(lll) oxide(l) or boric acid (2) are reacted with carbon in resistively heated furnaces at 2400°C (as in SiC-manufacture) ... 

Fine particulate tetraboron carbide is produced by the reduction of boron(III) oxide with magnesium or aluminum in the presence of carbon ... 

Hexagonal boron(lll) nitride is produced by reacting boron(Ill) oxide with ammonia (1) or nitrogen and carbon (2)... 

A very pure crystalline boron(lll) nitride is obtained by reacting boron(III) oxide with carbon and nitrogen at 1800 to I900°C ... 

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