Boron gaseous

This compound, which contains atoms arranged tetrahedrally around the boron atom, can readily be isolated from a mixture of dimethyl ether and boron trichloride. On occasions a chlorine atom, in spite of its high election affinity, will donate an electron pair, an example being found in the dimerisation of gaseous monomeric aluminium chloride to give the more stable Al2Clg in which each aluminium has a tetrahedral configuration ... 

Commercial boron trifluoride is usually approximately 99.5% pure. The common impurities are air, siUcon tetrafluoride, and sulfur dioxide. An excellent procedure for sampling and making a complete analysis of gaseous boron trifluoride has been developed (57). 

Examination of possible systems for boron isotope separation resulted in the selection of the multistage exchange-distillation of boron trifluoride—dimethyl ether complex, BF3 -0(CH3 )2, as a method for B production (21,22). Isotope fractionation in this process is achieved by the distillation of the complex at reduced pressure, ie, 20 kPa (150 torr), in a tapered cascade of multiplate columns. Although the process involves reflux by evaporation and condensation, the isotope separation is a result of exchange between the Hquid and gaseous phases. 

For adding dopiag impurities duriag vapor-phase growth, a gaseous or easily vaporizable Hquid compound is metered, added to the siUcon source gas stream, and reduced along with the siUcon compound. Typical examples are diborane, 2 phosphine, and boron tribromide, BBr. ... 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

Boron 800-1 050 (Halide) 1. Gaseous 2. Semi- gaseous 3. Pack 4. Salt-bath electrolysis Up to 500 /im Matrix plus borides Brittle Hardness up to 1 500 HV Heat treatment acceptable ... 

Therefore we should expect in the gaseous state to find molecules such as BeH2 and BeF2. These molecules have been detected. On the other hand, beryllium has the trouble boron has, only in a double dose. It has two vacant valence orbitals. As a result, BeH2 and BeF2 molecules, as such, are obtained only at extremely high temperatures (say, above 1000°K). At lower temperatures these vacant valence orbitals cause a condensation to a solid in which these orbitals can participate in bonding. We shall discuss these solids in the next chapter. 

The plasma jet can be cooled rapidly just prior to coming in contact with the substrate by using a blast of cold inert gas fed into an annular fixture. Gaseous boron or phosphorus compounds can be introduced into the gas feed for the deposition of doped-semiconduc-tor diamond. 

Unlike bonding, direct boride deposition does not require a reaction with the substrate to form the boride. Both boron and metal atoms are supplied as gaseous compounds. 

Because the breadth of chemical behavior can be bewildering in its complexity, chemists search for general ways to organize chemical reactivity patterns. Two familiar patterns are Br< )nsted acid-base (proton transfer) and oxidation-reduction (electron transfer) reactions. A related pattern of reactivity can be viewed as the donation of a pair of electrons to form a new bond. One example is the reaction between gaseous ammonia and trimethyl boron, in which the ammonia molecule uses its nonbonding pair of electrons to form a bond between nitrogen and boron ... 

Boron trifluoride, sulphur and disulphur dichlorides, phosphorus trichloride in the liquid state cause potassium to combust. The same is true for phosphorus pentachloride in the solid state. In the latter case the same accident happened with gaseous halide. The same is also true for the bromide analogues of these compounds. 

Boron ignites in gaseous chlorine or fluorine at ambient temperature, attaining incandescence in fluorine [ 1 ]. Powdered boron reacts spontaneously with the halogens from fluorine to iodine at 20, 400, 600 and 700° C respectively [2],... 

Mellor, 1941, Vol. 2, 292 1956, Vol. 2, Suppl. 1, 380 1943, Vol. 11, 26 Liquid chlorine at —34°C explodes with white phosphorus, and a solution in heptane at 0°C ignites red phosphorus. Boron, active carbon, silicon and phosphorus all ignite in contact with gaseous chlorine at ambient temperature. Arsenic incandesces on contact with liquid chlorine at —34°C, and the powder ignites when sprinkled into the gas at ambient temperature. Tellurium must be warmed slightly before incandescence occurs. 

The procedure described here involves the use of copper, rather than mercury, as a chlorine-getter. In this case, presumably, the principal reaction is heterogeneous in nature and involves the attack of metallic copper by gaseous boron trichloride, according to the equation ... 

A 2-1. three-necked flask is equipped with a stirrer, a 500-ml. dropping funnel protected by a calcium chloride drying tube, and a reflux condenser topped with a potassium hydroxide drying tube. The reaction vessel is cooled in an ice-salt bath and is charged with 500 ml. of dry pentane and 293 g. (6.5 mols) of anhydrous dimethylamine. A solution of 117.2 g. (1 mol) of boron trichloride in 400 ml. of pentane, prepared by passing the gaseous chloride into chilled pentane, is added slowly with... 

Although most of the fluorine calorimetry has been done with the elements, it has been used to burn oxides, carbides, nitrides, and chal-cogenides and hence determine their heats of formation. In some instances it has proved superior to oxygen bomb calorimetry. Thus the oxidation of boron tends to be incomplete because of oxide coating, whereas fluorination produces gaseous boron trifluoride without surface inhibition. A summary of modem fluorine calorimetry results is assembled in Table III. 

Similar treatment of binding energies for gaseous compounds of boron, nitrogen, oxygen, phosphorus, and sulfur leads to the following relations. 

Application of the equivalent cores method to solid compounds is slightly more complicated, requires additional assumptions, and is therefore less accurate than the application to gaseous compounds. However, fairly good correlations have been obtained for solid compounds of boron, carbon, nitrogen, and iodine20. The correlations were restricted, because of the nature of the assumptions involved, to molecular compounds or to compounds in which the core-ionized atoms are in anions. 

Examination of Fig. 9.4 for the B-N2 system reveals that BN decomposes into gaseous nitrogen and liquid boron. Since these elements are in their standard states at 1 atm and the decomposition temperature, the A/fy must equal the enthalpy of formation All" of the BN at the decomposition temperature. Indeed, the A/fy (300kJ/mol) calculated by the means described agrees with the value of AH°T (300kJ/mol) given in the JANAF tables, as it should. The same condition holds for the Si-N2 system. 

In a high-temperature atmosphere created by the combustion of a host hydrocarbon fuel, there will be an abundance of hydroxyl radicals. Thus, boron monoxide reacts with hydroxyl radicals to form gaseous metaboric oxide HOBO. 

It is postulated that HOBO then reacts with BO to form gaseous boron oxide hydride, HBO, and boron dioxide, B02 (OBO). 

After the gaseous reaction system is established, the B203 diffuses back to the nascent boron surface to form BO, just as C02 diffuses back to the carbon surface to form CO. The reaction is... 

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