Ammonium Bifluoride - Wikipedia

Ammonium bifluoride

Names
IUPAC name Ammonium bifluoride
Other names Ammonium acid fluoride Ammonium hydrofluoride Ammonium difluoride Ammonium hydrogendifluoride Ammonium hydrogen difluoride
Identifiers
CAS Number	1341-49-7 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	21241205 N
ECHA InfoCard	100.014.252
EC Number	215-676-4
PubChem CID	14935
UNII	C2M215358O
UN number	1727
CompTox Dashboard (EPA)	DTXSID9029645
InChI InChI=1S/F2H.H3N/c1-3-2;/h;1H3/q-1;/p+1 NKey: XIONBZYFLSJNBW-UHFFFAOYSA-O N InChI=1/2FH.H3N/h2*1H;1H3Key: KVBCYCWRDBDGBG-UHFFFAOYAG
SMILES [NH4+].F[H-]F [F-].F.[NH4+]
Properties
Chemical formula	[NH4][HF2]
Molar mass	57.044 g·mol−1
Appearance	Colourless crystals
Density	1.50 g cm−3
Melting point	126 °C (259 °F; 399 K)
Boiling point	240 °C (464 °F; 513 K)(decomposes)
Solubility in water	63g/(100 ml) (20 °C)
Solubility in alcohol	slightly soluble
Refractive index (nD)	1.390
Structure
Crystal structure	Cubic, related to the CsCl structure
Coordination geometry	[NH4]+ cation: tetrahedral[HF2]− anion: linear
Hazards
GHS labelling:
Pictograms	[1]
Hazard statements	H301, H314[1]
Precautionary statements	P280, P301+P310, P305+P351+P338, P310[1]
NFPA 704 (fire diamond)	3 0 0
Related compounds
Other cations	potassium bifluoride
Related compounds	ammonium fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Chemical compound

Ammonium bifluoride is an inorganic compound with the formula [NH4][HF2] or [NH4]F·HF. In solid form, it is a white, crystalline salt. It is typically produced from ammonia and hydrogen fluoride.

Ammonium bifluoride is toxic and corrosive. In industry, it etches glass and has been considered as a chemical intermediate for hydrofluoric acid production.

Structure

[edit]

Ammonium bifluoride, as its name indicates, contains an ammonium cation ([NH4]+), and a bifluoride (or hydrogen difluoride) anion ([HF2]−). The triatomic bifluoride anion features a strong three-center four-electron bond (specifically, a symmetrical hydrogen bond) with a bond energy greater than 155 kJ/mol,[2] and an H-F length of 114 pm.[3]

In solid form ([NH4][HF2]), ammonium biflouride is similar to other fluoride salts.[4] Its crystal system is orthorhombic,[5] with each cation coordinated with four anions in a tetrahedron (and vice versa). Hydrogen atoms in the ammonium ion form hydrogen bonds with the fluorine atoms, and in the resulting structure, N-H-F are roughly colinear.[6][7] As a result of these hydrogen bonds, this crystal structure varies from those of other bifluoride salts, such as potassium bifluoride and rubidium bifluoride.[5]

Production and applications

[edit]

Ammonium bifluoride is a component of some etchants. It attacks the silica component of glass:

SiO2 + 4 [NH4][HF2] → SiF4 + 4 [NH4]F + 2 H2O

Potassium bifluoride is a related, more commonly used etchant.

Ammonium bifluoride has been considered as an intermediate for the production of hydrofluoric acid from hexafluorosilicic acid. Hexafluorosilicic acid ammonolyzes to give ammonium fluoride, which thermally decomposes to the bifluoride:

H2[SiF6] + 6 NH3 + 2 H2O → SiO2 + 6 [NH4]F 2 [NH4]F → NH3 + [NH4][HF2]

The resulting ammonium bifluoride is converted to sodium bifluoride, which thermally decomposes to release HF.[8]

Ammonium bifluoride is also used as an additive in tin-nickel plating processes as the fluoride ion acts as a complexing agent with the tin, allowing for greater control over the resulting composition and finish.[citation needed]

Stability and toxicity

[edit]

Ammonium bifluoride crystals are unstable, and decompose rapidly when exposed to air.[6]

Ammonium bifluoride is toxic to consume and a skin corrosion agent. Upon exposure to skin, rinsing with water followed by a treatment of calcium gluconate is required.[1] In water, ammonium bifluoride exists in chemical equilibrium with hydrofluoric acid and heating releases hydrogen fluoride gas.[9] Consequently, there is an equivalent toxicological risk as is present with hydrofluoric acid, and the same safety precautions apply.[10][9]

Ammonium bifluoride is used in some automotive wheel cleaning products. Ammonium bifluoride products are often considered a safer alternative to hydrofluoric acid, yet still pose clear risks to the handler.[10] Many users unaware of the danger have experienced injuries.[11] Professional Car Washing and Detailing magazine considers ammonium bifluoride, ammonium fluoride, and hydrofluoric acid all "too dangerous for any use in a car wash environment,"[12] and a 2015 report from the U.S. Centers for Disease Control and Prevention concurs.[13]

References

[edit]

1. ^ a b c d Sigma-Aldrich Co., Ammonium bifluoride. Retrieved on 2013-07-20.
2. ^ Emsley, J. (1980) Very Strong Hydrogen Bonds, Chemical Society Reviews, 9, 91–124. doi:10.1039/CS9800900091
3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
4. ^ "Ammonium bifluoride". PubChem. Retrieved 17 September 2024.
5. ^ a b Troyanov, S. I. (2005). "Crystal Structure Refinement of Bifluorides MHF2 (M = Na, NH4, Rb). Crystal Structures of Rb5F4(HF2) × 2H2O and RbF × H2O". Crystallography Reports. 50 (5): 773–778. doi:10.1134/1.2049394. Retrieved 17 September 2024.
6. ^ a b McDonald, T. R. R. (1960). "The electron-density distribution in ammonium bifluoride". Acta Crystallogr. 13 (2): 113–124. Bibcode:1960AcCry..13..113M. doi:10.1107/S0365110X60000261.
7. ^ "ICSD Entry: 14140". Cambridge Structural Database: Access Structures. Cambridge Crystallographic Data Centre. Retrieved 2022-06-25.
8. ^ Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307. ISBN 3527306730.
9. ^ a b National Industrial Chemicals Notification and Assessment Scheme (April 17, 2020). "Bifluorides: Human health tier II assessment" (PDF). Department of Health (Australia). Retrieved February 8, 2023.
10. ^ a b Genuino, Homer C.; Opembe, Naftali N.; Njagi, Eric C.; McClain, Skye; Suib, Steven L. (2012). "A review of hydrofluoric acid and its use in the car wash industry". Journal of Industrial and Engineering Chemistry. 18 (5): 1529–1539. doi:10.1016/j.jiec.2012.03.001. ISSN 1226-086X.
11. ^ Gormley, James (May 29, 2001). "The truth about ammonium bifluoride". Professional Car Washing and Detailing. Archived from the original on 2001-05-29.
12. ^ Cook, Ryan (October 9, 2013). "The Five Factors of Clean: Chemistry, Part 1". Professional Car Washing and Detailing. Retrieved February 8, 2023.
13. ^ Woodie, Maria (December 1, 2015). "OSHA gives employees the right to know". Professional Car Washing and Detailing. Retrieved February 8, 2023.

v t e Fluorine compounds
v t e Salts and covalent derivatives of the fluoride ion HF ?HeF2 LiF BeF2 BFBF3B2F4+BO3 CF4CxFy+CO3 NF3FN3N2F2NFN2F4NF2?NF5+N+NO3 OF2O2F2OFO3F2O4F2?OF4 F2 Ne NaF MgF2 AlFAlF3 SiF4 P2F4PF3PF5+PO4 S2F2SF2S2F4SF3SF4S2F10SF6+SO4 ClFClF3ClF5 ?ArF2?ArF4 KF CaFCaF2 ScF3 TiF2TiF3TiF4 VF2VF3VF4VF5 CrF2CrF3CrF4CrF5?CrF6 MnF2MnF3MnF4?MnF5 FeF2FeF3FeF4 CoF2 CoF3 CoF4 NiF2NiF3NiF4 CuFCuF2?CuF3 ZnF2 GaF2GaF3 GeF2GeF4 AsF3AsF5 Se2F2SeF4SeF6+SeO3 BrFBrF3BrF5 KrF2?KrF4?KrF6 RbF SrFSrF2 YF3 ZrF2ZrF3ZrF4 NbF4NbF5 MoF4MoF5MoF6 TcF4TcF5 TcF6 RuF3RuF4RuF5RuF6 RhF3RhF4RhF5RhF6 PdF2Pd[PdF6]PdF4?PdF6 Ag2FAgFAgF2AgF3 CdF2 InFInF3 SnF2SnF4 SbF3SbF5 TeF4?Te2F10TeF6+TeO3 IFIF3IF5IF7+IO3 XeF2XeF4XeF6?XeF8 CsF BaF2   LuF3 HfF4 TaF5 WF4WF5WF6 ReF4ReF5ReF6ReF7 OsF4OsF5OsF6?OsF7?OsF8 IrF2IrF3IrF4IrF5IrF6 PtF2Pt[PtF6]PtF4PtF5PtF6 AuFAuF3Au2F10?AuF6AuF5•F2 Hg2F2HgF2?HgF4 TlFTlF3 PbF2PbF4 BiF3BiF5 PoF2PoF4PoF6 AtF?AtF3?AtF5 RnF2?RnF4?RnF6 FrF RaF2   LrF3 Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og ↓ LaF3 CeF3CeF4 PrF3 PrF4 NdF2 NdF3 NdF4 PmF3 SmF SmF2 SmF3 EuF2 EuF3 GdF3 TbF3 TbF4 DyF2 DyF3 DyF4 HoF3 ErF3 TmF2 TmF3 YbF2 YbF3 AcF3 ThF2ThF3ThF4 PaF4PaF5 UF3UF4UF5UF6 NpF3NpF4NpF5NpF6 PuF3PuF4PuF5PuF6 AmF2AmF3AmF4?AmF6 CmF3CmF4 ?CmF6 BkF3 BkF4 CfF3 CfF4 EsF3 EsF4?EsF6 Fm MdF3 No
PF−6, AsF−6, SbF−6 compounds	AgPF6 HPF6 KPF6 LiPF6 NaPF6 NH4PF6 TlPF6 KAsF6 LiAsF6 NaAsF6 HSbF6 KSbF6 LiSbF6 NaSbF6
AlF2−5, AlF3−6 compounds	Cs2AlF5 Li3AlF6 (NH4)3[AlF6] K3AlF6 Na3AlF6
chlorides, bromides, iodides and pseudohalogenides	BaClF BrSO3F Br(SO3F)3 CFN ClFO2 PbFBr PbFCl SiIBrClF SrFCl
SiF2−6, GeF2−6 compounds	BaGeF6 Li2GeF6 BaSiF6 Na2[SiF6] (NH4)2SiF6 K2[SiF6] Li2SiF6
Oxyfluorides	AcOF BrOF3 BrO2F BrO3F C2F4O C7H5FO ClOF3 ClO2F3 CrOF4 ErOF HoOF LaOF NdOF NpO2F2 OsOF5 PrOF PuOF PuO2F2 SmOF TbOF TcO3F ThOF2 UO2F2 VOF3 WOF4 YOF
Organofluorides	CBrF3 CBr2F2 CBr3F CClF3 CCl2F2 CCl3F CFNO3S CF2O CF3I CHF3 CH2F2 CH3F C2Cl3F3 C2H3F C3H5F C6H5F C6H11F C7H5F3 C15F33N
with transition metal, lanthanide, actinide, ammonium	(NH4)3CrF6 NH4F (NH4)3FeF6 (NH4)3GaF6 (NH4)2GeF6 (NH4)3InF6 NH4NbF6 (NH4)2SnF6 NH4TaF6 (NH4)3VF6 (NH4)2ZrF6 CsXeF7 Li2SnF6 Li2TiF6 LiWF6 Li2ZrF6 K2NbF7 K2TaF7 K2TiF6 K2ZrF6 Na2TiF6 Na2ZrF6 Rb2TiF6
nitric acids	FNO FNO2 FNO3
bifluorides	KHF2 NaHF2 NH4HF2
thionyl, phosphoryl, and iodosyl	FN3O2S F2OS3 F2OS F3OP PSF3 IOF3 IO3F F2O6S2 F2O5S2 FClO5S2 ISO3F IOF5 IO2F IO2F3 BrFO2S I3SO3F S3O8F2
Chemical formulas

v t e Ammonium salts
Inorganic salts	monatomic anions NH4F (NH4)2S NH4Cl (NH4)2Se NH4Br NH4I oxyanions NH4NO2 NH4NO3 CaNH4PO4 (NH4)2CO3 (NH4)4UO2(CO3)3 (NH4)HCO3 NH4H2AsO4 NH4BrO3 NH4ClO NH4OCN NH4B5O8 (NH4)3PO4 NH4PH2O2 (NH4)2HPO4 (NH4)H2PO4 NH4IO4 (NH4PO4)n(OH)2 NH4NaHPO4 (NH4)2SO3 (NH4)2SO4 (NH4)Al(SO4)2·12H2O (NH4)2Fe(SO4)2·6H2O NH4Fe(SO4)2·12H2O NH4SO3NH2 (NH4)HSO4 (NH4)2S2O8 (NH4)2S2O3 NH4ClO3 NH4ClO4 (NH4)2Mg(SO4)2 NH4VO3 Nd(NH4)2(NO3)5 (NH4)2CrO4 (NH4)2Cr2O7 NH4MnO4 (NH4)3AsO4 NH4BrO4 (NH4)2MoO4 (NH4)6Mo7O24 (NH4)3Mo12PO40 NH4IO3 (NH4)2Ce(NO3)6 (NH4)8Ce2(SO4)8·4H2O (NH4)10H2W12O42·4H2O NH4ReO4 (NH4)2SeO4 (NH4)2TeO4 other anions NH4BF4 NH4N3 NH4CN NH4[Au(CN)2] (NH4)HF2 (NH4)2SeBr6 (NH4)3AlF6 NH4SbF6 NH4AsF6 (NH4)3CrF6 (NH4)3FeF6 (NH4)3GaF6 (NH4)2GeF6 (NH4)3InF6 NH4NbF6 (NH4)2PtF6 (NH4)2ReF6 (NH4)2SnF6 NH4TaF6 (NH4)2UF6 (NH4)3VF6 (NH4)SiF6 (NH4)HS NH4SCN (NH4)2ZnCl4 (NH4)2MoS4 NH4I3 (NH4)2PtBr6 (NH4)2SnBr6 (NH4)2TeCl6 (NH4)2IrCl6 (NH4)2OsCl6 (NH4)2PtCl6 (NH4)2ReCl6 (NH4)2PdCl6 (NH4)2PbCl6 (NH4)3RhCl6 (NH4)2SeCl6 (NH4)2SnCl6 (NH4)4[Fe(CN)6] (NH4)3VS4 (NH4)2S5 (NH4)4[HgBr6] (NH4)2[PtI6] NH4AuCl4 (NH4)2PdCl4 (NH4)3AsS4 (NH4)2WS4 (NH4)2[PtCl4]
Organic salts	Aluminon Ammonium acetate Ammonium adipate Ammonium alginate Ammonium benzoate Ammonium bituminosulfonate Ammonium butyrate Ammonium carbamate Ammonium caprylate Ammonium cinnamate Ammonium citrate Ammonium diethyl dithiophosphate Ammonium ferric citrate Ammonium formate Ammonium fumarate Ammonium glutamate Ammonium heptadecanoate Ammonium itaconate Ammonium lactate Ammonium lauryl sulfate Ammonium laurate Ammonium malate Ammonium malonate Ammonium mandelate Ammonium myristate Ammonium nicotinate Ammonium nonanoate Ammonium oleate Ammonium oxalate Ammonium picrate Ammonium palmitate Ammonium perfluorononanoate Ammonium picolinate Ammonium propionate Ammonium salicylate Ammonium stearate Ammonium succinate Ammonium tartrate Ammonium thioglycolate Ammonium valerate Cupferron Ferric ammonium oxalate Murexide