Hydrogen boron trichloride system

This paper basically represents a feasibility study of the deposition of boron from a glow discharge system produced in a boron trichloride-hydrogen medium. Feasibility of the basic concept has been conclusively... 

Since boron trichloride reacts with many lubricants to form hydrogen chloride, the diboron tetrachloride synthesis is carried out in a grease-free system. A mercury float-valve vacuum system4 depicted in Fig. 15 is employed here. The U-traps have a capacity of 50 ml. without plugging and tubes A and B have... 

Substitution of the hydrogen of many other aromatic compounds is controllable, but the problem of site selectivity still limits the synthetic utility of this reaction (Table 9). In an attempt to improve selectivity the fluorination of chlorobenzene was investigated in the presence of Lewis acids (Table 10). The addition of the Lewis acid is found to increase both conversion and selectivity. The best results are obtained in the presence of 0.9 equivalents of boron trichloride the effect of the boron trichloride is explained by the formation of a complex 7 with the fluorine, which is the fluorinating species. Large amounts of Lewis acid are required due to the formation of a stable complex between the boron trichloride and the fluoride formed as the fluorination progresses which effectively removes the catalyst from the system. ... 

A general method for the cleavage of 4,5-dihydroisoxazoles is hydrogenation over Raney nickel in the presence of an acid or a Lewis acid, such as boric acid ° or boron trichloride. The products are normally p-hydroxy ketones but in the case of compound (35), which was prepared as an intermediate in the construction of the AB-ring system of forskolin, reduction over Raney nickel gave an isolable imine (36). ... 

The cyclization can be carried out with halogenated amines, and substitution products of the new ring systems can also be obtained in the conventional way, by nitration, etc. Similar compounds can be prepared directly by using arylboron dichlorides in place of boron trichloride in the procedure indicated above. The parent borazarene derivatives, with hydrogen attached to boron, can be made from the B-hydroxy compounds with lithium aluminum hydride in the presence of aluminum chloride. N-Alkyl derivatives can be made either by using N-alkyl derivatives of the aminobiphenyls as starting materials, or by N-alkylation of the unsubstituted compounds via their N-lithio derivatives. Apart from their inherent interest, compounds of this type can serve as intermediates in various syntheses. Thus benzocinnolines and 2,2 -dihydroxybiphenyls can be obtained from derivatives of 2-aminobiphenyl. ... 

Zinc borate in halogenated systems, such as flexible PVC, is known to increase markedly the amount of char formed during polymer combustion whereas the addition of antimony, a vapour phase flame retardant, has little effect on char formation. The hydrogen chloride released from PVC thermal degradation can react with the zinc borate [6] to form zinc hydroxychloride and zinc chloride as well as boric oxide and boron trichloride (equation 5). 

First, the preparations of powder and sintered specimens are mentioned. Polycrystalline boron phosphide powder (27) material was prepared by the reduction of a boron tribromide-phosphorus trichloride mixture with hydrogen in a gas flow system in a fused silica tube furnace at about 1100°C. An excess of phosphorus trichloride was used to maintain the stoichiometry of the deposit. The deposition rate was approximately 2 g/h. 

The deposition of boron phosphide by CVD was carried out in a gas flow system by the thermal decomposition of diborane-phosphine mixtures in a hydrogen atmosphere and the thermal reduction of boron tribromide-phosphorus trichloride mixtures with hydrogen (37). The hydrides are thermodynamically unstable at room temperature and decompose rapidly at above 500°C, which tends to promote homogeneous nucleation by pyrolysis in the gas phase. The halides are thermally more stable than the hydrides, and higher substrate temperatures may be used in the thermal reduction process with essentially no gas-phase reactions. At high substrate temperatures, a phosphorus pressure equal to or greater than the vapor pressure of boron phosphide must be present over the substrate surface to maintain the stoichiometry of the deposit. 

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