Nitrogen difluoride

Nitrogen difluoride
Identifiers


CAS Number	3744-07-8^[1]
3D model (JSmol)	Interactive image
ChemSpider	121681
PubChem CID	138039
CompTox Dashboard (EPA)	DTXSID90190888
InChI InChI=1S/F2N/c1-3-2 Key: BBZREMAMWBDNHH-UHFFFAOYSA-N
SMILES [N](F)F
Properties
Chemical formula	NF₂
Molar mass	52.004 g·mol⁻¹
Related compounds
Related nitrogen fluorides	Nitrogen trifluoride Dinitrogen tetrafluoride Nitrogen monofluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N (what is ^YN ?) Infobox references

Chemical compound

Nitrogen difluoride, also known as difluoroamino, is a reactive radical molecule with formula NF₂. This small molecule is in equilibrium with its dimer tetrafluorohydrazine.^[2]

N₂F₄ ⇌ 2 NF₂

As the temperature increases the proportion of NF₂ increases.^[3]

The molecule is unusual in that it has an odd number of electrons, yet is stable enough to study experimentally.^[4]

Properties

The energy needed to break the N–N bond in N₂F₄ is 20.8 kcal/mol (87 kJ/mol), with an entropy change of 38.6 eu.^[5] For comparison, the dissociation energy of the N–N bond is 14.6 kcal/mol (61 kJ/mol) in N₂O₄, 10.2 kcal/mol (43 kJ/mol) in N₂O₂, and 60 kcal/mol (250 kJ/mol) in N₂H₄. The enthalpy of formation of N₂F₄ (Δ_fH) is 8.227 kcal/mol (34.421 kJ/mol).^[6]

At room temperature N₂F₄ is mostly associated with only 0.7% in the form of NF₂ at 5 mmHg (670 Pa) pressure. When the temperature rises to 225 °C, it mostly dissociates with 99% in the form of NF₂.^[5]

In NF₂, the N–F bond length is 1.3494 Å and the angle subtended at F–N–F is 103.33°.^[7]

In the infrared spectrum the N–F bond in NF₂ has a symmetrical stretching frequency of 1075 cm⁻¹. This compares to 1115 cm⁻¹ in NF, 1021 cm⁻¹ in NF₃ and 998 cm⁻¹ in N₂F₄.^[5]

The microwave spectrum shows numerous lines due to spin transitions, with or without nuclear spin transitions. The lines form set of two triplets for antisymmetric singlet, or two triplets of triplets for symmetric triplet. Lines appear around 14–15, 24, 25, 26, 27, 28–29, 33, 60, 61, 62, and 65 GHz. The rotational constants for the NF₂ molecule are A = 70496 MHz, B = 11872.2 MHz, and C = 10136.5 MHz. The inertial defect Δ = 0.1204 m_u·Å². The centrifugal distortion constants are τ_aaaa = −7.75, τ_bbbb = −0.081, τ_aabb = 0.30, and τ_abab = −0.13.^[7]

The dipole moment is 0.13 D (4.5×10⁻³¹ C·m).^[7]

The ground electronic state of the molecule is ²B₁.^[7]

The gas is often contaminated with NO or N₂O.^[5]

Use

Nitrogen difluoride is formed during the function of a xenon monofluoride excimer laser. Nitrogen trifluoride is the halide carrier gas, which releases fluoride ions when impacted by electrons:^[1]

NF₃ + e⁻ → NF₂ + F⁻

The free fluoride ion goes on to react with xenon cations.^[1]

Nitrogen difluoride can be consumed further to yield nitrogen monofluoride.^[1]

NF₂ + e⁻ → NF + F⁻

References

^ ^a ^b ^c ^d Trainor, Daniel W. (February 1989). "Electron dissociative attachment to nitrogen difluoride radicals". The Journal of Physical Chemistry. 93 (3): 1134–1136. doi:10.1021/j100340a022.
^ Jäger, Susanne; von Jouanne, Jörn; Keller-Rudek, Hannelore; Koschel, Dieter; Kuhn, Peter; Merlet, Peter; Rupecht, Sigrid; Vanecek, Hans; Wagner, Joachim (1986). Koschel, Dieter; Kuhn, Peter; Merlet, Peter; Ruprecht, Sigrid; Wagner, Joachim (eds.). F Fluorine: Compounds with Oxygen and Nitrogen. Gmelin Handbook of Inorganic Chemistry. Vol. 4. Berlin: Springer. p. 162. doi:10.1007/978-3-662-06339-2. ISBN 978-3-662-06341-5. Retrieved 29 August 2015.
^ Johnson, Frederic A.; Colburn, Charles B. (July 1961). "The Tetrafluorohydrazine-Difluoroamino Radical Equilibrium". Journal of the American Chemical Society. 83 (14): 3043–3047. doi:10.1021/ja01475a018.
^ Brown, R. D.; Burden, F. R.; Hart, B. T.; Williams, G. R. (1973). "The electronic structure of the NF₂ radical". Theoretica Chimica Acta. 28 (4): 339–353. doi:10.1007/BF00529015. S2CID 100649705.
^ ^a ^b ^c ^d Bohn, Robert K.; Bauer, Simon Harvey (February 1967). "An electron diffraction study of the structures of NF₂ and N₂F₄". Inorganic Chemistry. 6 (2): 304–309. doi:10.1021/ic50048a024. molecule dimensions and angles
^ "Nitrogen difluoride NF₂(g)".
^ ^a ^b ^c ^d Brown, R.D.; Burden, F.R.; Godfrey, P.D.; Gillard, I.R. (August 1974). "Microwave spectrum of NF₂". Journal of Molecular Spectroscopy. 52 (2): 301–321. Bibcode:1974JMoSp..52..301B. doi:10.1016/0022-2852(74)90121-0.

Extra reading

Goodfriend, P.L.; Woods, H.P. (January 1964). "The absorption spectrum of NF₂". Journal of Molecular Spectroscopy. 13 (1–4): 63–66. Bibcode:1964JMoSp..13...63G. doi:10.1016/0022-2852(64)90055-4.
Jacox, Marilyn E.; Milligan, Dolphus E.; Guillory, William A.; Smith, Jerry J. (August 1974). "Matrix-isolation study of the vacuum-ultraviolet photolysis of NF₃". Journal of Molecular Spectroscopy. 52 (2): 322–327. Bibcode:1974JMoSp..52..322J. doi:10.1016/0022-2852(74)90122-2.
Heidner, R. F.; Helvajian, Henry; Koffend, J. Brooke (August 1987). "Tunable UV laser photolysis of NF₂: Quantum yield for NF(a¹Δ) production" (PDF). The Journal of Chemical Physics. 87 (3): 1520–1524. Bibcode:1987JChPh..87.1520H. doi:10.1063/1.453262.
Papakondylis, Aristotle; Mavridis, Aristides (December 1993). "Electronic and geometrical structure of the NF₂ radical" (PDF). Chemical Physics Letters. 216 (1–2): 167–172. Bibcode:1993CPL...216..167P. doi:10.1016/0009-2614(93)E1254-E.
Cai, Z.-L.; Sha, G.-H.; Zhang, C.-H.; Huang, M.-B. (March 1991). "Ab initio study of low-lying electronic states of the NF₂ radical". Chemical Physics Letters. 178 (2–3): 273–278. Bibcode:1991CPL...178..273C. doi:10.1016/0009-2614(91)87068-M.