Boron trichloride

Description

Boron trichloride is a colorless, acid gas that fumes in the presence of moist air. It is packaged in steel cylinders as a liquid under its own vapor pressure of 19.1 psia (132 kPa, abs) at 70°F (21.1°C). It reacts with water or moist air to produce hydrochloric and boric acid.

Description

Boron trichloride (BCl3) is a Lewis acid typically used for the demethylation of methyl ethers. Boron trichloride is not as reactive as boron tribromide (BBr3), but this lower reactivity can sometimes be beneficial for controlling selectivity. At room temperature boron trichloride is gas, but usually it is purchased and used as a 1M solution in DCM.

Chemical properties

Boron trichloride is a colorless gas with a pungent odor. It reacts violently with water, and on decomposition and hydrolysis yields hydrochloric and boric acid. It has a pungent, highly irritating odor. Occupational exposure to boron and boron compounds can occur in industries that produce special glass, washing powder, soap and cosmetics, leather, cement, etc.

The Uses of Boron trichloride

Boron trichloride is a Lewis acid, forming stable addition compounds with such donors as ammonia and the amines and is used in the laboratory to promote reactions that liberate these donors. The compound is important industrially as a source of pure boron (reduction with hydrogen) for the electronics industry. It is also used for the preparation of boranes by reaction with metal hydrides.

The Uses of Boron trichloride

manufacture of and purification of boron; as catalyst for organic reactions; in semiconductors; in bonding of iron, steels; in purification of metal alloys to remove oxides, nitrides and carbides.

The Uses of Boron trichloride

Boron trichloride is used in the refining of aluminum, copper, magnesium, and zinc to remove oxides, nitrides, and carbides trom the molten metal. Carbon monoxide, hydrogen, and nitrogen can be removed from an aluminum melt by treating with boron trichloride. It also improves the tensile strength of aluminum and will allow remelting without a major change in the grain structure.
The electronic industry benefits trom boron trichloride in many applications. It is used in the production of optical fibers, as a p-type dopant for thermal diffusion in silicon, and for ion implantation.

Definition

A fuming liquid made by passing dry chlorine over heated boron. It is rapidly hydrolysed by water: BCl₃ + 3H₂O → 3HCl + H₃BO₃ As there are only three pairs of shared electrons in the outer shell of the boron atom, boron halides form very stable addition compounds with ammonia by the acceptance of a lone electron pair in a coordinate bond to complete a shared octet.

Preparation

Boron trichloride can be prepared by high temperature chlorination of boron trioxide, boric acid, metal borates or other boron compounds. Chlorine, hydrogen chloride, phosgene, silicon tetrachloride, metal chlorides, carbontetrachloride, sulfuryl chloride and phosphorus tri- and pentachlorides are some of the common chlorinating agents. The reaction is carried out at temperatures varying between 400° to 1,400°C, depending on the reactants used. In commercial processes, carbon is generally used to reduce boron oxide during its chlorination. Some of the preparative reactions are outlined below:
B₂O₃ + 2PCl₃ → 2BCl₃ + P2O₃
2B₂O₃ + 3CCl₄ → 4BCl₃ + 3CO₂
B2O₃ + 3C+ 3Cl₂ → 2BCl₃ + 3CO
2B(OH)₃ +3C + 3Cl₂ → 2BCl₃ + 3CO + 3H₂O
B₂O₃ + 3C + 6HCl → 2BCl₃ + 3CO + 3H₂
Na₂B₄O₇ + 7C + 14HCl → 4BCl₃ + 2NaCl + 7CO + 7H₂
2KBF₄ + 3MgCl₂ → 2BCl₃ + 2KF + 3MgF₂
Boron trichloride may also be obtained by high temperature chlorination of boron:
2B + 3Cl₂ → 2BCl₃
B + 3AgCl → BCl₃ + 3Ag
In the laboratory, boron trichloride may be made at ordinary temperatures by the reaction of boron trifluoride with aluminum chloride:
BF3 + AlCl₃ → BCl₃ + AlF₃

What are the applications of Application

One of the most important uses of Boron trichloride is in the preparation of boron fibers ( Fibers, 13. Refractory Fibers). Typically an electrically heated tungsten filament is passed through a chamber containing BCl3 and hydrogen. The BCl3 is reduced, and boron is deposited on the filament, producing a stiff, strong boron fiber.Boron trichloride, like the trifluoride, has been used as a Lewis acid catalyst in organic synthesis in the polymerization of olefins and phosphazines, as well as in catalysis of other organic reactions. Boron trichloride is also used in plasma etching of aluminum and silicon, in semiconductor manufacturing, and as a source of boron for chemical vapor deposition. Steel is boronized by contacting it with a reactive mixture of hydrogen, hydrocarbons, and BCl3 at high temperatures.

General Description

Boron trichloride appears as a colorless gas with a pungent odor. Fumes irritate the eyes and mucous membranes. Corrosive to metals and tissue and is toxic. Under prolonged exposure to fire or intense heat, the containers may rupture violently and rocket. Used as a catalyst in chemical manufacture, in soldering fluxes, and for many other uses.

Air & Water Reactions

Fumes in air, including moisture in air and soil, to form hydrochloric acid [Merck 11th ed. 1989]. Reacts vigorously with water and forms hydrochloric acid fumes and boric acid.

Reactivity Profile

Boron trichloride vigorously attacks elastomers and packing materials. Contact with Viton, Tygon, Saran and natural and synthetic rubbers is not recommended. Highly corrosive to most metals in the presence of moisture. Reacts energetically with nitrogen dioxide/dinitrogen tetraoxide, aniline, phosphine, triethylsilane, or fat and grease [Mellor 5:132 1946-47]. Reacts exothermically with chemical bases (examples: amines, amides, inorganic hydroxides).

Health Hazard

Boron trichloride is highly irritating and corrosive to the eyes, skin, and mucous membranes of the respiratory and gastrointestinal tracts.may cause severe burns to skin. May result in marked fluid and electrolyte loss and shock. On acute inhalation, boron trichloride result in sneezing, hoarseness, choking, laryngitis, and respiratory tract irritation along with bleeding of the nose and gums, ulceration of the nasal and oral mucosa, bronchitis, pneumonia, dyspnea, chest pain, and pulmonary edema.

Fire Hazard

When heated to decomposition, Boron trichloride emits toxic fumes of chlorides. Boron trichloride will react with water or steam to produce heat, and toxic and corrosive fumes. In hot water, decomposes to hydrochloric acid and boric acid. Fumes and hydrolyzes in moist air to form hydrochloric acid and oily, irritating corrosives. Avoid aniline, hexafluorisopropylidene amino lithium, nitrogen dioxide, phosphine, grease, organic matter, and oxygen. Nitrogen peroxide, phosphine, fat or grease react energetically with Boron trichloride . Oxygen and Boron trichloride react vigorously on sparking. Boron trichloride and aniline react violently in the absence of a coolant or diluent. Stable.

Potential Exposure

Used in refining of aluminum, magnesium, copper alloys, and in polymerization of styrene. Manufacture and purification of boron; catalyst in organic reactions; semiconductors; bonding of iron or steel; purification of metal alloys to remove oxides, nitrides, and carbides; chemical intermediate for boron filaments; soldering flux; electrical resistors; and extinguishing magnesium fires in heat treating furnaces.

Physiological effects

Boron trichloride is irritating and corrosive to all living tissue. Exposure of skin tissue to higher concentrations of boron trichloride or the liquid can cause hydrochloric acid bums and skin lesions resulting in tissue destruction and scarring. Chemical pneumonitis (deep lung inflammation) and pulmonary edema (abnormal fluid buildup in the lungs) result trom excessive exposure to the lower respiratory tract and deep lung. Bums to the eyes result in lesions and possible loss of vision. Symptoms of exposure include tearing of eyes, coughing, labored breathing, and excessive salivary and sputum formation.
ACGIH has not established a Threshold Limit Value (TLV?) for boron trichloride. It is recommended that compliance with the 5 ppm ceiling limit (TLV-C) for hydrogen chloride be used.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contactsthe skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately.If this chemical has been inhaled, remove fromexposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing hasstopped and CPR if heart action has stopped. Transferpromptly to a medical facility. When this chemical hasbeen swallowed, get medical attention immediately. Do notinduce vomiting. Medical observation is recommended for24
48 h after breathing overexposure, as pulmonaryedema may be delayed. As first aid for pulmonary edema,a doctor or authorized paramedic may consider administering a corticosteroid spray.

storage

Boron trichloride cylinders should be protected from physical damage. The cylinders should be stored upright and fi rmly secured to prevent falling or being knocked over, in a cool, dry, well-ventilated area of non-combustible construction away from heavily traffi cked areas and emergency exits

Shipping

This chemical requires a shipping label of“POISON GAS, CORROSIVE.” It falls in Hazard Class 2.3(poison) hazard Zone B, with no Packing Group cited.[19, 20]Special precautions: Cylinders must be transported in asecure upright position, in a well-ventilated truck. It is aviolation of transportation regulations to refill compressedgas cylinders without the express written permission of theowner.

Purification Methods

Purify it (from chlorine) by passage through two mercury-filled bubblers, then fractionally distil it under a slight vacuum. In a more extensive purification the nitrobenzene addition compound is formed by passage of the gas over nitrobenzene in a vacuum system at 10o. Volatile impurities are removed from the crystalline yellow solid by pumping at -20o, and the BCl3 is recovered by warming the addition compound at 50o. Passage through a trap at -78o removes entrained nitrobenzene, the BCl3 finally condensing in a trap at -112o [Brown & Holmes J Am Chem Soc 78 2173 1956]. Also purify it by condensing it into a trap cooled in acetone/Dry-ice, where it is pumped for 15minutes to remove volatile impurities. It is then warmed, recondensed and again pumped. [Gamble Inorg Synth III 27 1950.] TOXIC.

Incompatibilities

Incompatible with lead, graphiteimpregnated asbestos, potassium, sodium. Vigorously attacks elastomers, packing materials, natural and synthetic rubber; viton, tygon, saran, silastic elastomers. Avoid aniline, hexafluorisopropylidene amino lithium, nitrogen dioxide, phosphine, grease, organic matter; and oxygen. Nitrogen peroxide, phosphine. Fat or grease react vigorously with boron trichloride. It reacts with water or steam to produce heat, boric acid, and corrosive hydrochloric acid fumes. Oxygen and boron trichloride react vigorously on sparking. Attacks most metals in the presence of moisture.

Waste Disposal

Return refillable compressed gas cylinders to supplier. Nonrefillable cylinders should be disposed of in accordance with local, state, and federal regulations. Allow remaining gas to vent slowly into atmosphere in an unconfined area or exhaust hood. Refillabletype cylinders should be returned to original supplier with any valve caps and outlet plugs secured and valve protection caps in place.

Precautions

Boron trichloride vigorously attacks elastomers and packing materials, natural and synthetic rubbers. It also reacts energetically with nitrogen dioxide/dinitrogen tetraoxide, aniline, phosphine, triethylsilane, or fat and grease. It reacts exothermically with chemical bases such as amines, amides, and inorganic hydroxides. Occupational workers should use gloves of neoprene or butyl rubber, PVC or polyethylene, safety goggles, or glasses and face shield, and safety shoes.

GRADES AVAILABLE

Boron trichloride is available for commercial and industrial purposes with a minimum purity of99.9 percent by weight.
Boron trichloride is also available in ultra high purity grades for use in the electronics industry. Gas purity guidelines have been developed and published by the Semiconductor Equipment and Materials International and can be found in the Book ofSEMI Standards.