Title: Boron Trifluoride
CAS Registry Number: 7637-07-2
Molecular Formula: BF3
Molecular Weight: 67.81
Percent Composition: B 15.94%, F 84.05%
Literature References: A strong Lewis acid. Prepn: Swinehart, US 2148514, US 2196907 (1939, 1940 both to Harshaw Chemical); Booth, Wilson, Inorg. Synth. 1, 21 (1939); Kwasnik in Handbook of Preparative Inorganic Chemistry Vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 219-222; Wiesboeck, US 3690821 (1972 to U.S. Steel). Dihydrate: McGrath et al., J. Am. Chem. Soc. 66, 1263 (1944). Reviews: Booth, Martin, Boron Trifluoride and Its Derivatives (John Wiley & Sons, 1949), 296 pp; Booth in Fluorine Chemistry Vol. 1, J. Simons, Ed. (Academic Press, New York, 1950) pp 201-224; Topchiev et al., Boron Fluoride and Its Compounds as Catalysts in Organic Chemistry (Pergamon Press, 1959) 326 pp; Martin in Kirk-Othmer Encyclopedia of Chemical Technology Vol. 9 (Interscience, New York, 2nd ed., 1966) pp 554-562; Massey, Adv. Inorg. Chem. Radiochem. 10, 1-152 (1967). Review of toxicology and human exposure: Toxicological Profile for Boron (PB93-110674, 1992) 110 pp.
Properties: Colorless gas. Pungent, suffocating odor. Forms dense white fumes in moist air. bp -127.1°. bp -100.4°. d4 (-100.4°; liq) 1.57. d (gas at STP) 3.07666 g/l. Soly in water (0°): 332 g/100 g; some hydrolysis occurs to form fluoboric and boric acids. Soly in anhydrous H2SO4: 1.94 g/100 g acid. Forms solid complex with nitric acid (HNO3.2BF3). Sol in most saturated and halogenated hydrocarbons and in aromatic compds. Polymerizes unsaturated molecules. Easily forms coordination complexes with molecules having at least one unshared pair of electrons. Reacts with incandescence when heated with alkali metals or alkaline earth metals except magnesium.
Boiling point: bp -127.1°; bp -100.4°
Density: d4 (-100.4°; liq) 1.57; d (gas at STP) 3.07666 g/l
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin, nose, respiratory system; epistaxis; burns to eyes and skin. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 32. See also Patty's Industrial Hygiene and Toxicology vol. 2B, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 3rd ed., 1981) pp 2996-2999.
Use: To protect molten magnesium and its alloys from oxidation; as a flux for soldering magnesium; as a fumigant; in ionization chambers for the detection of weak neutrons. By far the largest application of boron trifluoride is in catalysis with and without promoting agents.