Hydrogen difluoride anion
3D model (JSmol)
CompTox Dashboard (EPA)
|Conjugate acid||Hydrogen fluoride|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure and bonding
The bifluoride ion has a linear, centrosymmetric structure (D∞h symmetry), with a F−H bond length of 114 pm. The bond strength is estimated to be greater than 155 kJ/mol. In molecular orbital theory, the atoms are modeled to be held together by a 3-center 4-electron bond.
Acid-base properties and salts
In the reaction
2 + H+ ⇌ 2 HF
the ion is acting as a Brønsted–Lowry base. This reaction can occur in non-aqueous solution. On the other hand, in the reaction
2 + H2O ⇌ 2 F− + H3O+
- MF + HF → M(HF2) M = K+ or NH+
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- Denne, W.A.; Mackay, M.F. (1971). "Crystal structure of p-toluidinium bifluoride". Journal of Crystal and Molecular Structure. 1 (5): 311–318.
- Emsley, J. (1980). "Very Strong Hydrogen Bonds". Chemical Society Reviews. 9: 91–124. doi:10.1039/CS9800900091.
- Pimentel, G. C. The Bonding of Trihalide and Bifluoride Ions by the Molecular Orbital Method. J. Chem. Phys. 1951, 19, 446-448. doi:10.1063/1.1748245