Beryllium fluoride
| Names | |
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| IUPAC name
Beryllium fluoride
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| Other names
Beryllium difluoride
Difluoroberyllane | |
| Identifiers | |
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3D model (JSmol)
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| ChEBI |
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| ChemSpider |
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| ECHA InfoCard | 100.029.198 Edit this at Wikidata |
PubChem CID
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| RTECS number |
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| UNII |
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CompTox Dashboard (EPA)
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| Properties | |
| BeF2 | |
| Molar mass | 47.01 g/mol hygroscopic |
| Appearance | colorless, glassy lumps |
| Density | 1.986 g/cm3 |
| Melting point | 554 °C (1,029 °F; 827 K)[1] |
| Boiling point | 1,169 °C (2,136 °F; 1,442 K)[2] |
| very soluble | |
| Solubility | sparingly soluble in alcohol |
| Structure | |
| Trigonal, α-quartz | |
| P3121 (No. 152), Pearson symbol hP9[3] | |
a = 473.29 pm, c = 517.88 pm
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| Linear | |
| Thermochemistry | |
Heat capacity (C)
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1.102 J/K or 59 J/mol K |
Std molar
entropy (S⦵298) |
45 J/mol K |
Std enthalpy of
formation (ΔfH⦵298) |
-1028.2 kJ/g or -1010 kJ/mol |
Gibbs free energy (ΔfG⦵)
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-941 kJ/mol |
| Hazards[6] | |
| GHS labelling: | |
| Corrosive Acute Toxicity Reproductive toxicity, target organ toxicity, carcinogen, aspiration hazard Environment, aquatic toxicity | |
| Danger | |
| H301, H305, H311, H314, H315, H319, H330, H335, H372, H411 | |
| P201, P202, P260, P264, P270, P271, P273, P280, P281, P284, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P312, P314, P320, P321, P322, P330, P361, P363, P391, P403+P233, P405, P501 | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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90 mg/kg (oral, rat) 100 mg/kg (oral, mouse)[5] |
| NIOSH (US health exposure limits): | |
PEL (Permissible)
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TWA 0.002 mg/m3 C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be)[4] |
REL (Recommended)
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Ca C 0.0005 mg/m3 (as Be)[4] |
IDLH (Immediate danger)
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Ca [4 mg/m3 (as Be)][4] |
| Safety data sheet (SDS) | InChem MSDS |
| Related compounds | |
Other anions
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Beryllium chloride Beryllium bromide Beryllium iodide |
Other cations
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Magnesium fluoride Calcium fluoride Strontium fluoride Barium fluoride Radium fluoride |
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Beryllium fluoride is the inorganic compound with the formula Be F 2. This white solid is the principal precursor for the manufacture of beryllium metal. Its structure resembles that of quartz, but BeF2 is highly soluble in water.
Properties
[edit ]Beryllium fluoride has distinctive optical properties. In the form of fluoroberyllate glass, it has the lowest refractive index for a solid at room temperature of 1.275. Its dispersive power is the lowest for a solid at 0.0093, and the nonlinear coefficient is also the lowest at 2 ×ばつ 10−14.
Structure and bonding
[edit ]
The structure of solid BeF2 resembles that of cristobalite. Be2+ centers are four coordinate and tetrahedral and the fluoride centers are two-coordinate.[7] The Be-F bond lengths are about 1.54 Å.[8] Analogous to SiO2, BeF2 can also adopt a number of related structures. An analogy also exists between BeF2 and AlF3: both adopt extended structures at mild temperature.
Gaseous and liquid BeF2
[edit ]Gaseous beryllium fluoride adopts a linear structure, with a Be-F distance of 143 pm.[9] BeF2 reaches a vapor pressure of 10 Pa at 686 °C, 100 Pa at 767 °C, 1 kPa at 869 °C, 10 kPa at 999 °C, and 100 kPa at 1172 °C.[10] Molecular BeF2 in the gaseous state is isoelectronic to carbon dioxide.
As a liquid, beryllium fluoride has a tetrahedral structure. The density of liquid BeF2 decreases near its freezing point, as Be2+ and F− ions begin to coordinate more strongly with one another, leading to the expansion of voids between formula units.[11]
Production
[edit ]The processing of beryllium ores generates impure Be(OH)2. This material reacts with ammonium bifluoride to give ammonium tetrafluoroberyllate:
- Be(OH)2 + 2 (NH4)HF2 → (NH4)2BeF4 + 2 H2O
Tetrafluoroberyllate is a robust ion, which allows its purification by precipitation of various impurities as their hydroxides. Heating purified (NH4)2BeF4 gives the desired product:
- (NH4)2BeF4 → 2 NH3 + 2 HF + BeF2
In general the reactivity of BeF2 ions with fluoride are quite analogous to the reactions of SiO2 with oxides.[12]
Applications
[edit ]Reduction of BeF2 at 1300 °C with magnesium in a graphite crucible provides the most practical route to metallic beryllium:[9]
- BeF2 + Mg → Be + MgF2
The Beryllium chloride is not a useful precursor because of its volatility. [citation needed ]
Niche uses
[edit ]Beryllium fluoride is used in biochemistry, particularly protein crystallography as a mimic of phosphate. Thus, ADP and beryllium fluoride together tend to bind to ATP sites and inhibit protein action, making it possible to crystallise proteins in the bound state.[13] [14]
Beryllium fluoride forms a basic constituent of the preferred fluoride salt mixture used in liquid-fluoride nuclear reactors. Typically beryllium fluoride is mixed with lithium fluoride to form a base solvent (FLiBe), into which fluorides of uranium and thorium are introduced. Beryllium fluoride is exceptionally chemically stable, and LiF/BeF2 mixtures (FLiBe) have low melting points (360–459 °C) and the best neutronic properties of fluoride salt combinations appropriate for reactor use. MSRE used two different mixtures in the two cooling circuits.
Safety
[edit ]Beryllium compounds are highly toxic. The increased toxicity of beryllium in the presence of fluoride has been noted as early as 1949.[15] The LD50 in mice is about 100 mg/kg by ingestion and 1.8 mg/kg by intravenous injection.
References
[edit ]- ^ "Beryllium Fluoride". American Elements. Retrieved 10 July 2023.
- ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0487-3.
- ^ Wright, Albert F.; Fitch, Andrew N.; Wright, Adrian C. (1988). "The preparation and structure of the α- and β-quartz polymorphs of beryllium fluoride". Journal of Solid State Chemistry. 73 (2): 298. Bibcode:1988JSSCh..73..298W. doi:10.1016/0022-4596(88)90113-2.
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0054". National Institute for Occupational Safety and Health (NIOSH).
- ^ "Beryllium compounds (as Be)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^ "Beryllium Difluoride". PubChem. National Institute of Health. Retrieved October 13, 2017.
- ^ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
- ^ Pallavi Ghalsasi, Prasanna S. Ghalsasi, "Single Crystal X-Ray Structure of BeF2: α-Quartz" Inorg. Chem., 2011, 50 (1), pp 86–89. doi:10.1021/ic101248g
- ^ a b Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Vapor pressure, physics.nyu.edu, p. 6-63, from Ohe, S. (1976) Computer Aided Data Book of Vapor Pressure, Data Book Publishing Co., Tokyo.
- ^ Agarwal, M.; Chakravarty C (2007). "Waterlike Structural and Excess Entropy Anomalies in Liquid Beryllium Fluoride". J. Phys. Chem. B. 111 (46): 13294–300. doi:10.1021/jp0753272. PMID 17963376.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ Reiko Kagawa; Martin G. Montgomery; Kerstin Braig; Andrew G. W. Leslie; John E. Walker (2004). "The structure of bovine F1-ATPase inhibited by ADP and beryllium fluoride". The EMBO Journal. 23 (5): 2734–2744. doi:10.1038/sj.emboj.7600293. PMC 514953 . PMID 15229653.
- ^ Bigay J.; Deterre P.; Pfister C.; Chabre M. (1987). "Fluoride complexes of aluminium or beryllium act on G-proteins as reversibly bound analogues of the gamma phosphate of GTP". The EMBO Journal. 6 (10): 2907–2913. doi:10.1002/j.1460-2075.1987.tb02594.x. PMC 553725 . PMID 2826123.
- ^ Fluoride in Drinking Water: A Scientific Review of EPA's Standards. The National Academies Press. 2006. pp. 51–52. doi:10.17226/11571. ISBN 978-0-309-10128-8.