Boron compounds toxicity

Boron. The principal materials used are borax [1303-96-4] sodium pentaborate, sodium tetraborate, partially dehydrated borates, boric acid [10043-35-3] and boron frits. Soil appHcation rates of boron for vegetable crops and alfalfa are usually in the range of 0.5—3 kg/hm. Lower rates are used for more sensitive crops. Both soil and foHar appHcation are practiced but soil appHcations remain effective longer. Boron toxicity is not often observed in field appHcations (see Boron compounds). 

Powdered or fine dust of elemental boron is explosive in air and toxic if inhaled. Several of the compounds of boron are very toxic if ingested or if they come in contact with the skin. This is particularly true of the boron compounds used for strong insecticides and herbicides. 

Volatile boron compounds, especially boranes, are usually more toxic than boric acid or soluble borates (Table 29.9) (NAS 1980). However, there is little commercial production of synthetic boranes, except for sodium borohydride — one of the least toxic boranes (Sprague 1972). Boron trifluoride is a gas used as a catalyst in several industrial systems, but on exposure to moisture in air, it reacts to form a stable dihydride (Rusch etal. 1986). Eor boric oxide dusts, occupational exposures to 4.1 mg/m (range 1.2 to 8.5) are associated with eye irritation dryness of mouth, nose and throat sore throat and cough (Garabrant et al. 1984). 

Various boron compounds have been used as rocket fuels, diamond substitutes, and additives to aluminum alloys to improve electrical and thermal conductivity, as well as for grain refining. Boron hydrides are sensitive to shock and can detonate easily. Boron halides ate corrosive and toxic. 

Caution. Although neither reactants nor products are spontaneously flammable, the boron compounds are toxic and should be handled with care. The pyrolysis bulb should be carefully inspected to ensure that it is completely free from cracks or imperfections that could result in an implosion upon evacuation. The volume of the bulb is such that the gas pressure at pyrolysis temperature is no more than 1.5 atm. If the scale of this synthesis is changed, the bulb size should be altered accordingly. 

Caution. l,3-Diaza-2-boracycloalkanes are moisture-sensitive and react readily with protonic materials. Alcohols, in particular, may occasionally cause an explosive solvolysis reaction on contact with these heterocycles. The compounds should be handled under dry inert gas (nitrogen or argon) to avoid their contamination. The possible toxicity of boron compounds has not yet been explored. 

SAFETY PROFILE A poison and strong irritant. See also FLUORIDES and BORON COMPOUNDS. When heated to decomposition it emits very toxic fumes of F", NOx, and NH3. 

SAFETY PROFILE Confirmed carcinogen. Ignites and then explodes in air or on contact with water. Upon decomposition it emits toxic fumes of BeO and BOx. See also BERYLLIUM COMPOUNDS and BORON COMPOUNDS. 

SAFETY PROFILE Moderately toxic by ingestion and intraperitoneal routes. An eye and skin irritant. A pesticide. Mixed with CaO and put into fused CaCb, the mixture incandesces. See also BORON COMPOUNDS. 

SAFETY PROFILE A poison. Corrosive. A skin, eye, and mucous membrane irritant. Dangerous may explode when heated. This and other boron halides react with water or steam to produce toxic and corrosive fumes and may explode. Incompatible with K Na. When heated to decomposition it emits toxic fumes of Br . See also BORON COMPOUNDS and HYDROBROMIC ACID. 

SAFETY PROFILE A poison by inhalation. A strong irritant. See also BORON COMPOUNDS and FLUORIDES. A nonflammable gas. Dangerous when heated to decomposition or upon contact with water or steam, will produce toxic and corrosive fumes of F". Incompatible with... 

DOT CLASSIFICATION 4.1 Label Flammable Solid, Poison SAFETY PROFILE Poison by inhalation, ingestion, skin contact, and intraperitoneal routes. Ignites in O2 at 100°C. Forms impact-sensitive explosive mixtures with ethers (e.g., dioxane) and halocarbons (e.g., carbon tetrachloride). Incompatible with dimethyl sulfoxide. When heated to decomposition it emits toxic fumes of boron oxides. See also BORON COMPOUNDS and BORANES. 

SAFETY PROFILE Poison by intravenous route. Moderately toxic by intraperitoneal route. An experimental teratogen. A skin irritant. When heated to decomposition it emits toxic fumes of boron. See also BORANES and BORON COMPOUNDS. 

Flammable Liquid SAFETY PROFILE A poison by intravenous route. Moderately toxic by ingestion. An eye irritant. A flammable liquid and dangerous fire hazard when exposed to heat, flame, or oxidizers. Can react vigorously with oxidizing materials. To fight fire, use foam, CO2, dry chemical. See also ESTERS and BORON COMPOUNDS. 

A45. R. M. Adams, ed., Boron, Metallo-boron Compounds and Boranes. Wiley (Interscience), New York, 1964. 765 pp. Mainly inorganic boron chemistry, but organometallic compounds are described briefly in Chapters 6 and 7. Chapter 8 contains a section (7 pp.) on the toxicity of organoboron compounds. 

The dotted arrows on the transmetallation step 243 show only what joins to what and are not intended as a serious mechanism. Indeed a better mechanism might involve addition of RO to the boron atom before transmetallation. This process can be used to couple aryl to aryl, vinyl to vinyl, and aryl to vinyl (either way round ). As boron compounds are much less toxic than tin compounds, the Suzuki coupling is often preferred industrially. Because each partner in the coupling reaction is marked in a different way - one with a boron atom and one with a halide - we can be sure that we shall get cross coupling reactions only. 

Diborane is one of three most toxically efficient boron compounds. Its LD50 is 30 to 90 mg m during a 4-hour exposure [77]. In the course of higher exposure, manifestations of the irritation of the central nervous system, damage to the kidneys, and lung oedema are observed. Concentrations exceeding 2 to 4 ppm [78] can be detected by the smell and a 15-minute exposure to 159 ppm is lethal [79]. 

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