Boron liquid sources

Boron trifluoride is a highly moisture-sensitive gas (31). It is utilized in esterification, ether formation, Friedel-Crafts alkylation and acylation, and Lewis acid-catalyzed Diels-Alder reactions. A more widely used, easy-to-handle and convenient liquid source of BF3 is boron trifluoride etherate [BF3-0(C2H5)2] (32). Its main usage as catalyst is in the direct esterification of all types of acids, rearrangements, aldol condensation, and Lewis acid-catalyzed Diels-Alder reactions. It is the most frequently used acid in epoxide ring opening and rearrangement (33). 

Olefins are carbonylated in concentrated sulfuric acid at moderate temperatures (0—40°C) and low pressures with formic acid, which serves as the source of carbon monoxide (Koch-Haaf reaction) (187). Liquid hydrogen fluoride, preferably in the presence of boron trifluoride, is an equally good catalyst and solvent system (see Carboxylic acids). 

Imaging SIMS. Steeds et al. (1999) included this technique in their study of the distribution of boron introduced into diamond, where it is a well-established dopant that controls the electrical conductivity. SIMS was performed with a field-emission liquid gallium ion source interfaced to a magnetic sector mass spectrometer capable of about 0.1 pm spatial resolution. 

Boron trifluoride gas may be used in place of the etherate. In this case a fritted-glass gas-dispersion tube that extends below the liquid surface replaces the second addition funnel. Boron trifluoride gas (0.20 mole, 4.48 1.) is passed through the solution as the peroxytrifluoroacetic acid is added. The boron trifluoride may be metered into the mixture through a calibrated flowmeter containing carbon tetrachloride as the indicator liquid. Alternatively, a premeasured quantity of boron trifluoride may be displaced by carbon tetrachloride from a gas bulb. The yield is approximately the same regardless of the source of boron trifluoride. 

The submitters employed 75 g. (0.5 mole) of the liquid 1 2 boron trifluoride-acetic acid complex obtained from Harshaw Chemical Company. Since the checkers were unable to obtain this complex from a commercial source, they prepared the solid 1 1 complex following published directions.3 4 A 2-1. threenecked flask is fitted with a mechanical stirrer, a gas outlet tube, and a gas inlet tube extending to the bottom of the flask. A solution of 230 ml. of acetic acid in 750 ml. of 1,2-dichloro-ethane is added to the flask and a stream of boron trifluoride gas is passed through the reaction flask while the solution is stirred and cooled with an ice bath. After approximately 1 hour, when the mixture is saturated, the addition of boron trifluoride is stopped and the insoluble 1 1 boron trifluoride-acetic acid complex is rapidly collected on a filter, washed with 200 ml. of... 

A mixture of 30.0 g. (0.5 mole) of anhydrous isopropyl alcohol and 65.0 g. (0.5 mole) of freshly distilled ethyl acetoacetate is placed in a 500-ml. round-bottomed three-necked flask equipped with a mercury-sealed stirrer, a gas inlet tube terminating about 1 cm. above the surface of the liquid, a gas outlet tube connected with a calcium chloride drying tube, and a thermometer (Note 2). The gas inlet tube is connected to a source of boron fluoride (Note 3), and an ice bath is applied to the reaction flask when the temperature of the stirred mixture has fallen to approximately 0° the stream of boron fluoride is started and adjusted so that the temperature of the mixture does not exceed 7°. The addition of... 

In recent years, the great majority of solid rockets have utilized composite propellants. Most composite propellants are based on a solid oxidizer and a curable liquid polymeric binder. The binder also serves as fuel. Optionally, metallic fuels such as aluminum or boron may also be used.45 The propellant components are mixed together, and then the binder is cured to give the tough, flexible, elastomeric (rubbery thermoset) solid propellant required for modem missile use. An excellent source of information on the formulation of solid propellants is a report by Oberth.46... 

Analogous to epoxides, aziridines can be prepared by the methylenation of imines. In this case, ethyl diazoacetate is the most common source of carbenes. For example, the imine derived from p-chlorobenzaldehyde 148 is converted to the c/j-aziridinyl ester 149 upon treatment with ethyl diazoacetate in the presence of lithium perchlorate <03TL5275>. These conditions have also been applied to a reaction medium of the ionic liquid l-n-butyl-3-methylimidazolium hexafluorophosphate (bmimPFe) with excellent results <03TL2409>. An interesting enantioselective twist to this protocol has been reported, in which a diazoacetate derived from (TJ)-pantolactone 150 is used. This system was applied to the aziridination of trifluoromethyl-substituted aldimines, which were prepared in situ from the corresponding aminals under the catalysis of boron trifluoride etherate <03TL4011>. 

Boron is another possible p-type dopant. The incorporation of boron into silicon epitaxial layers grown from a tin melt has been studied by Baliga [15] and McCann [16]. Boron is provided via the silicon source wafer and its incorporation is a function of both time and temperature. Its segregation coefficient from liquid tin into solid silicon is temperature dependent and increases with temperature. Therefore, the content of boron into the layer will be maximum at the interface and minimum at the final surface. This doping gradient can be used to create a drift field in the base layer of the... 

The green colour comes from BO2 band spectrum. The boron mixture is used as an ignition composition in place of thermit, and the difference between the two lies in that the former ignites other compositions with its high temperature flame but the latter mainly with its high temperature liquid cinder. Amorphous boron is very expensive commercially, but it is very useful when the ignition surface of a composition cannot be pasted with thermit as in the case of a rocket propellant which must start without a delay. The boron mixture ignites very well from a relatively weak heat source such as a black powder flame. 

Thermalized neutrons are easily absorbed by many isotopes. Examples are " In, Cd, and Of these, the most practical to use is boron. It can be used in powder form or be dissolved in water or liquid wax. A very simple but effective shield for a source of fast neutrons is 0.15-0.30 m of wax or paraffin to which boron has been added. The thickness of this borated material may change, depending on the strength of the source and the amount of boron... 

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