Boron III Bromide

Bromine vapor is allowed to react with a large excess of commercial boron at 700°C. The apparatus used is represented schematically in Fig. 9. The reaction vessel (72) is a silica tube (4.5 cm. i.d., 90 cm. high). In the center of the tube is a silica grating (g) supported on a silica rod or tube. The reactor is heated by means of an electric furnace equipped with a temperature controller. The evaporation chamber (V) for the bromine and the condenser (C) for the product are 1-1. round-bottomed flasks. All stopcock joints are lubricated with a fluorinated grease. 

A 120-g. samplef of commercial boron (10 moles) is introduced as tablets (about 17-mm. diam., 10 mm. thick) onto the grating g of the reactor. With stopcock R2 closed, the boron charge is heated to 700-750°C. and degassed under vacuum, 

The product prepared in this way without the use of elemental bromine should be satisfactory for the starting material in Sec. B, but both the original preparation and the checking procedure used BBr, made by the direct reaction of boron and bromine as described herein. 

J 90-92% amphorous boron is available from the U.S. Borax Co., 412 Crescent Way, Anaheim, Calif. The checkers used boron from Matheson Coleman and Bell, P.O. Box 85, East Rutherford, N.J. 07073. 

Editor s note Very recently U.S. Borax announced the availability of boron ranging in purity from 98.0 to 99.7% with undefined crystal properties. 

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The a-rhombohedral form of boron (a-boron) was first reported by L. V. McCarty, J. S. Kasper, F. H. Horn, B. F. Decker, and A. E. Newkirk.1 Of the many allotropic forms of boron, it has the simplest structure.2 It may be prepared by the pyrolysis of boron(III) iodide on a tantalum filament at 800-1000°C., but the product is usually contaminated by other allotropic varieties of boron.1,4 Recently, Hagenmuller and Naslain showed that boron(III) bromide may be reduced by... 

Editor s note The synthesis of boron(III) bromide using the reaction between BF, and Al2Bt is described in Inorganic Syntheses, 3, 29 (1950). The pertinent equation is... 

Boron(III) bromide is obtained as a perfectly colorless liquid. It is rapidly hydrolyzed by atmospheric moisture.7,8... 

In 1895, Besson treated boron(III) bromide with phosgene for 12 h at 150 C to yield a mixture of COBr, (b.pt. 63-66 C) and COCIBr (b.pt. 35-37 C) [184]. However, Von Bartal [2126,2127] and Brochet [2127] both found that they could obtain neither COBr nor COCIBr from this procedure. 

Subazaporphyrin containing trifluoromethyl group 209 was prepared in a low yield (1.9 %) by cyclotrimerization of l,l,2-lricyano-2-(2-trifluoiomethylphenyl)ethylene 166b (see Scheme 41) in the presence of boron(III) bromide in chlorobenzene at... 

Shi and coworkers have reported that the reaction of benzaldehydes with but-3-yn-2-one in the presence of boron (III) bromide provides the a-bromo methylene aldol product (115) in high selectivity. This approach provides the analogous P-bromo Baylis-Hillman adducts (Equation 70) [73]. 

Ravina and coworkers have disclosed the use of boron (III) bromide to cleanly deprotect 2-MOM -pyridazinone (153) without affecting the double bond and furnish the deprotected pyridazinone (154) in almost quantitative yield (Equation 92) [94]. 

Aluminum trichloride is the most commonly used catalyst, although aluminum tribromide is more efficient.1 For the rearrangement of l-broino-2-chloro-1,L2-lrifluoroethane (3) to 2-bromo-2-chloro-l,l,l-trifhioroethane (4). none of the following Lewis acids are effective iron(III) chloride. iron(III) bromide, antimony(III) chloride, antimony(V) chloride. tin(IV) chloride, titanium(IV) chloride, zinc(II) chloride, and boron trifluoride-diethyl ether complex.1" ... 

The phosphorus (V) chloride-boron chloride complex has been prepared by the chlorination of the phosphorus(III) bromide-boron bromide complex at room temperature, by chlorinating an equimolar mixture of phosphorus (III)... 

R. C. Paul, S. C. Ahluwalia, S. K. Rehari, and S. Singh Pahil, Indian J. Chem., 3, 297 (1965). Nature of solutions of Lewis acids in acetic acid systems antimony (V) chloride, tin (IV) chlorine, tin (IV) bromide and boron (III) fluoride. 

Thallium(III), particularly as the trifluoroacetate salt, is also a reactive electrophilic metallating species, and a variety of synthetic schemes based on arylthallium intermediates have been devised.75 Arylthallium compounds are converted to chlorides or bromides by reaction with the appropriate cupric halide.76 Reaction with potassium iodide gives aryl iodides.77 Fluorides are prepared by successive treatment with potassium fluoride and boron trifluoride.78 Procedures for converting arylthallium compounds to nitriles and phenols have also been described.79... 

A ubiquitous co-catalyst is water. This can be effective in extremely small quantities, as was first shown by Evans and Meadows [18] for the polymerisation of isobutene by boron fluoride at low temperatures, although they could give no quantitative estimate of the amount of water required to co-catalyse this reaction. Later [11, 13] it was shown that in methylene dichloride solution at temperatures below about -60° a few micromoles of water are sufficient to polymerise completely some decimoles of isobutene in the presence of millimolar quantities of titanium tetrachloride. With stannic chloride at -78° the maximum reaction rate is obtained with quantities of water equivalent to that of stannic chloride [31]. As far as aluminium chloride is concerned, there is no rigorous proof that it does require a co-catalyst in order to polymerise isobutene. However, the need for a co-catalyst in isomerisations and alkylations catalysed by aluminium bromide (which is more active than the chloride) has been proved [34-37], so that there is little doubt that even the polymerisations carried out by Kennedy and Thomas with aluminium chloride (see Section 5, iii, (a)) under fairly rigorous conditions depended critically on the presence of a co-catalyst - though whether this was water, or hydrogen chloride, or some other substance, cannot be decided at present. 

The redistribution reaction in lead compounds is straightforward and there are no appreciable side reactions. It is normally carried out commercially in the liquid phase at substantially room temperature. However, a catalyst is required to effect the reaction with lead compounds. A number of catalysts have been patented, but the exact procedure as practiced commercially has never been revealed. Among the effective catalysts are activated alumina and other activated metal oxides, triethyllead chloride, triethyllead iodide, phosphorus trichloride, arsenic trichloride, bismuth trichloride, iron(III)chloride, zirconium(IV)-chloride, tin(IV)chloride, zinc chloride, zinc fluoride, mercury(II)chloride, boron trifluoride, aluminum chloride, aluminum bromide, dimethyl-aluminum chloride, and platinum(IV)chloride 43,70-72,79,80,97,117, 131,31s) A separate catalyst compound is not required for the exchange between R.jPb and R3PbX compounds however, this type of uncatalyzed exchange is rather slow. Again, the products are practically a random mixture. 

Improved versions of OLGA (versions II and III) enabled the applications of corrosive gases such as hydrogen chloride or hydrogen bromide, chlorine, thionyl chloride or boron tribromide vapor etc. This made it possible to synthesize volatile halides and measure their retention times in isothermal quartz columns. 

SULFICYLBIS (METHANE) (67-68-5) CjHjOS (CH3)2S0 Combustible liquid [explosion limits in air (vol %) 2.6 to 63.0 flashpoint 203°F/95°C oc autoignition temp 419°F/215°C Fire Rating 2]. Violent or explosive reaction with strong oxidizers, acryl halides, aryl halides and related compounds, alkali metals p-bromobenzoyl acetanilide, boron compounds, especially hydrides iodine pentafluoride, magnesium perchlorate, methyl bromide, perchloric acid, periodic acid, silver fluoride, sodium hydride, potassium permanganate. Forms powerfully explosive mixtures with metal salts of oxoacids [iron(III)nitrate, phosphonic acid, sodium perchlorate]. On small fires, use dry chemicals or COj extinguishers. 

Barium iodate 1-hydrate, synthesis 4 Indium(I) bromide, synthesis 6 Hexachlorodisiloxane, synthesis 7 Trichlorosilanethiol, synthesis 8 Tris(acetylacetonato)silicon chloride, synthesis 9 Titanium(III)chloride, synthesis 11 Bis[tris(acetylacetonato)titanium(IV)] hexachloro-titanate(IV), synthesis 12 Zirconium(IV) iodide, synthesis 13 (Triphenyl) aminophosphonium chloride, synthesis 19 (Dimethylamido)phosphoryl dichloride, synthesis 20 Bis(dimethylamido)phosphoryl chloride, synthesis 21 Trimeric and tetrameric phosphonitrilic bromides, synthesis 23 Phosphorus(V) chloride-boron trichloride complex, synthesis 24... 

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