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| | Diborane Basic information |
| | Diborane Chemical Properties |
| Melting point | -165°C | | Boiling point | -93°C | | density | 0.477 | | Fp | -90°C | | form | colorless gas | | Odor | Repulsive odor detectable at 1.8 to 3.5 ppm | | Water Solubility | Decomposes | | Merck | 13,3039 | | Exposure limits | TLV-TWA 0.11 mg/m3 (0.1 ppm) (ACGIH
and OSHA); IDLH 40 ppm (NIOSH). | | NIST Chemistry Reference | Diborane(6)(19287-45-7) | | EPA Substance Registry System | Diborane (19287-45-7) |
| | Diborane Usage And Synthesis |
| Description | Diborane is a colorless gas at room temperature
and atmospheric pressure. It has an unpleasant,
distinctive, sickly sweet odor. Diborane is a
highly flammable gas that forms a flammable
mixture with air over a range of 0.9 percent to
98 percent diborane (at 1 atm). Diborane bums
in air (or oxygen) with a blue to green flame.
Diborane is considered pyrophoric at room
temperature. The gas is easily ignited by a spark
or the heat of reaction with moisture in air.
Pure diborane is insensitive to mechanical
shock; however, shock and thermally sensitive
mixtures may be formed in the presence of impurities
such as oxygen, water, halogenated hydrocarbons,
and so on. Thermal decomposition
of diborane to hydrogen can result in excessive
pressure buildup. Vessels for containment
of diborane should be designed to contain
such resultant decomposition pressure. | | Chemical Properties | Diborane is a compressed, colorless, and flam-
mable gas. It has a nauseating, sickly sweet odor. | | Uses | Diborane is used as a rocket propellant, in thevulcanization of rubber, as a polymerizationcatalyst, as a reducing agent, in the synthesisof trialkyl boranes, and as a doping agent(Merck 1996). | | Uses | Diborane is commonly used in the electronics
industry for semiconductor doping by mixing
small concentrations with silane in the gas phase
prior to decomposition. When reacted with
silane and oxygen, diborane also produces the
cladding layers of wave guides for fiber optics
by chemical vapor deposition.
Other uses of diborane include the preparation
of boron nitride by the reaction of diborane
with ammonia, as a catalyst for polymerization,
and for the conversion of olefins to trialkyl boranes.
It is also used in the conversion of amines
to amine boranes and as a selective reducing
agent with carbonyl compounds such as aldehydes
and ketones to form alcohols. | | Uses | As catalyst for olefin polymerization; as rubber vulcanizer; as reducing agent; as flame-speed accelerator; in rocket propellants; in intermediate in preparation of the boron hydrides; in conversion of olefins to trialkylboranes and primary alcohols; as a doping gas. | | Air & Water Reactions | Highly flammable. Ignites spontaneously in moist air (forms hydrogen and boric acid), [Haz. Chem. Data (1966)]. Oxygen and Diborane form spontaneously explosive mixtures, [J. Amer. Chem. Soc. 76, 1997(1954)]. | | Reactivity Profile | Diborane is a colorless, air and moisture-sensitive gas, highly toxic. Diborane ignites in air. Diborane is very explosive when exposed to heat or flame, on contact with moisture Diborane produces hydrogen gas. Explosive reaction with benzene vapor, chlorine, nitric acid and tetravinyllead [Bretherick, 5th ed., 1995, p. 77]. Explosive reaction with dimethyl sulfoxide [Shriver, 1969, p. 209], violent reaction with halocarbon liquids used as fire extinguishants (e.g., carbon tetrachloride). Reaction with Al or Li produces complex hydrides that may ignite spontaneously in air [Haz. Chem. Data, 1975, p. 114]. | | Hazard | Diborane is pyrophoric and will ignite upon exposure to air. The boiling point is ?135°F and the flammable range is 0.8%–88% in air. The ignition temperature is 100° (37°C) to 140°F (60°C), and the flash point is 130°F (54°C). Diborane will react violently with halogenated fire-extinguishing agents, such as the halons. The four-digit UN identification number is 1911. The NFPA 704 designation is health 4, flammability 4, and reactivity 3. The white section of the diamond has a W with a slash through it, indicating water reactivity. | | Health Hazard | Animal studies indicate that exposure todiborane results in irritation and possibleinfection in respiratory passage. In additionto the acute poisoning of the lungs, this gasmay cause intoxication of the central nervoussystem. A 4-hour exposure to 60 ppm maybe lethal to mice, resulting in death frompulmonary edema. | | Health Hazard | Inhalation of diborane gas results in irritation of the respiratory tract and may result
in headache, cough, nausea, difficulty in breathing, chills, fever, and weakness. The
odor of diborane cannot be detected below the permissible exposure limit, so this
substance is considered to have poor warning properties. Overexposure to diborane
can cause damage to the central nervous system, liver, and kidneys. Death can result
from pulmonary edema (fluid in the lungs) and/or from lack of oxygen. Exposure to
diborane gas has not been found to have significant effects on the skin and mucous
membranes, but high concentrations can cause eye irritation, and contact with the
liquid can cause burns.
Chronic exposure to low concentrations of diborane may cause headache,
lightheadedness, fatigue, weakness in the muscles, and tremors. Repeated exposure
may produce chronic respiratory distress, particularly in susceptible individuals. An
existing dermatitis may also be worsened by repeated exposure to the liquid.
Diborane has not been shown to have carcinogenic or reproductive or developmental
effects in humans. | | Health Hazard | Boranes are highly toxic by inhalation, skin absorption or ingestion. They may produce acute or chronic poisoning. Diborane is an irritant to the lungs and kidneys. The primary effect of Diborane poisoning is lung congestion caused by local tissue irritation produced by the exothermic reaction of hydrolysis. | | Fire Hazard | Diborane will ignite spontaneously in moist air at room temperature. Also, Diborane reacts violently with vaporizing liquid-type extinguishing agents. Diborane hydrolyzes in water to hydrogen and boric acid. Incompatible with air, halogenated compounds, aluminum, lithium, active metals, oxidized surfaces, chlorine, fuming nitric acid, nitrogen trifluoride, oxygen, and phosphorus trifluoride. Avoid moist air, electrical sparks, open flames or any other heat source. Hazardous polymerization may occur. | | Fire Hazard | Diborane is a flammable gas that ignites spontaneously in moist air at room
temperature and forms explosive mixtures with air from 0.8% up to 88% by volume.
Diborane reacts with halogenated hydrocarbons, and fire extinguishing agents such
as Halon or carbon tetrachloride are therefore not recommended. Carbon dioxide
extinguishers should be used to fight diborane fires. Fires involving diborane
sometimes release toxic gases such as boron oxide smoke. | | Flammability and Explosibility | Diborane is a flammable gas that ignites spontaneously in moist air at room temperature and forms explosive mixtures with air from 0.8% up to 88% by volume. Diborane reacts with halogenated hydrocarbons, and fire extinguishing agents such as Halon or carbon tetrachloride are therefore not recommended. Carbon dioxide extinguishers should be used to fight diborane fires. Fires involving diborane sometimes release toxic gases such as boron oxide smoke. | | Materials Uses | Common metals are suitable as materials of
construction. These include the following metals
and metal alloys: chrome-molybdenum steel,
Type 300 stainless steel, brass, lead, Monel,
K-Monel, and nickel. Piping and appurtenances
for undiluted diborane must be designed by
experienced engineers and safety and fire protection specialists. Saran, polyethylene, Kel-F,
Teflon, graphite, and high-vacuum silicone
grease are satisfactory for use with diborane.
In addition to the ability of a material to withstand
chemical attack, the evaluation of materials
compatibility with diborane should also emphasize
the effect of the material on diborane
stability (as expressed by the decomposition
rate). The use of the following materials is not
recommended:
? Metal oxides
? Natural rubbers
? Neoprene
? Leak-lock
? Permatex
? Ordinary oil and grease
? Nordel 1145 RPT elastomer, unfilled and
Si02-filled
? silicon elastomer, unfilled and SiOrfilled
? CIS-4 polybutadiene elastomer, unfilled
and SiOrfilled | | Safety Profile | Poison by inhalation.
An irritant to skin, eyes, and mucous
membranes comparable to chlorine,
fluorine, arsine, and phosgene. The liquid
causes local inflammation, blisters, redness,
and swelling. Injuries to central nervous
system, liver, and hdneys have also been
produced in experimental animals. Sirmlar
observations have been reported in humans,
resulting at times in a reaction resembling
metal fume fever. Human exposure to
pentaborane has produced signs of severe
central nervous system irritation such as
drowsiness, dlzziness, visual disturbances,
muscle twitching, and in severe cases,
painful muscle spasm. Dangerously
flammable when exposed to heat or flame
or by chemical reaction. On contact with
moisture, hydrogen is usually evolved.
Highly explosive when exposed to heat or
flame. Explosive reaction with air,
tetravinyllead, O2 above 165℃, octanol
oxime + sodium hydroxide, benzene vapor,
HNO3Cl2. Violent reaction with halocarbon
liquids. Other boron hydrides evolve H2
upon contact with moisture or can
propagate a flame rapidly enough to cause
an explosion. Heat can cause these materials
to decompose violently or at least to evolve
H2. They also react with water or steam to
evolve hydrogen. Reaction with Al or Li
forms complex hydrides that may ignite
spontaneously in air. Powerful oxidlzing
agents, such as chlorine gas, etc., can react
violently with boron hydrides. Pentaborane
(stable) is spontaneously flammable in air.
See also BORANES and HYDRIDES. | | Potential Exposure | Diborane is used as the source of
boron in the semiconductor industry; as a catalyst for olefin
polymerization; a rubber vulcanizer; a reducing agent;
a flame-speed accelerator; a chemical intermediate for
other boron hydrides; as a doping agent; in rocket propel-
lants, and in the conversion of olefins to trialkyl boranes
and primary alcohols. | | Physiological effects | ACGIH recommends a Threshold Limit Value-Time-
Weighted Average (TLV-TWA) of 0.1
ppm (0.11 mg/m3
) for diborane. The TLVTWA
is the time-weighted average concentration
for a normal 8-hour workday and a 40-hour
workweek, to which nearly all workers may be
repeatedly exposed, day after day, without adverse
effect.
OSHA lists an 8-hour Time-Weighted Average-
Permissible Exposure Limit (TWA-PEL)
of 0.1 ppm (0.1 mg/m3
) for diborane. TWAPEL
is the exposure limit that shall not be exceeded
by the 8-hour time-weighted average in
any 8-hour work shift of a 40-hour workweek | | storage | diborane should be used only in a fume hood free of ignition sources and should be stored in a cold, dry, wellventilated area separated from incompatible substances and isolated from sources of sparks and open flames. | | Shipping | UN1911 Diborane, Hazard Class: 2.3; Labels:
2.3-Poisonous gas, 2.1-Flammable gas Inhalation Hazard
Zone A. Cylinders must be transported in a secure upright
position, in a well-ventilated truck. Protect cylinder and
labels from physical damage. The owner of the compressed
gas cylinder is the only entity allowed by federal law
(49CFR) to transport and refill them. It is a violation of
transportation regulations to refill compressed gas cylinders
without the express written permission of the owner. | | Incompatibilities | A strong reducing agent. Unstable above
8
C. The presence of contaminants may lower the autoigni-
tion temperature; ignition may take place at, or below,
room temperature. Diborane can polymerize, forming liquid
pentaborane (See P:0190). It ignites spontaneously in moist
air; and on contact with water, hydrolyzes exothermically
forming hydrogen and boric acid. Contact with halogenated
compounds (including fire extinguishers) may cause fire
and explosion. Contact with aluminum, lithium and other
active metals form hydrides which may ignite spontane-
ously. Incompatible with aluminum, carbon tetrachloride;
nitric acid; nitrogen trifluoride and many other chemicals.
Reacts with oxidized surfaces. Attacks some plastics,
rubber or coatings. | | Waste Disposal | Return refillable compressed
gas cylinders to supplier. Incineration with aqueous scrub-
bing of exhaust gases to remove B2O3 particulates. | | GRADES AVAILABLE | Diborane is sold in ambient or refrigerated cylinders
with a purity of 99 percent or greater. It
is commonly used in the electronics industry,
mainly in the form of dilute mixtures. |
| | Diborane Preparation Products And Raw materials |
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