Nitrogen difluoride explained

Nitrogen difluoride, also known as difluoroamino, is a reactive radical molecule with formula . This small molecule is in equilibrium with its dimer tetrafluorohydrazine.^[1]

As the temperature increases the proportion of increases.^[2]

The molecule is unusual in that it has an odd number of electrons, yet is stable enough to study experimentally.^[3]

Properties

The energy needed to break the N–N bond in is, with an entropy change of 38.6 eu.^[4] For comparison, the dissociation energy of the N–N bond is in , in , and in . The enthalpy of formation of (Δ_fH) is .^[5]

At room temperature is mostly associated with only 0.7% in the form of at pressure. When the temperature rises to 225 °C, it mostly dissociates with 99% in the form of .

In, the N–F bond length is 1.3494 Å and the angle subtended at F–N–F is 103.33°.^[6]

In the infrared spectrum the N–F bond in has a symmetrical stretching frequency of 1075 cm⁻¹. This compares to 1115 cm⁻¹ in NF, 1021 cm⁻¹ in and 998 cm⁻¹ in .^[4]

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 molecule are A =, B =, and C = . 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.^[6]

The dipole moment is 0.13 D .^[6]

The ground electronic state of the molecule is ²B₁.^[6]

The gas is often contaminated with NO or .^[4]

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:

The free fluoride ion goes on to react with xenon cations.

Nitrogen difluoride can be consumed further to yield nitrogen monofluoride.^[7]

Extra reading

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

Notes and References

1. Book: F Fluorine: Compounds with Oxygen and Nitrogen. Gmelin Handbook of Inorganic Chemistry. 4. 1986. Springer. Berlin. 978-3-662-06341-5. 10.1007/978-3-662-06339-2. 162. 29 August 2015. Koschel. Dieter. Jäger. Susanne. von Jouanne. Jörn. Keller-Rudek. Hannelore. Koschel. Dieter. Kuhn. Peter. Merlet. Peter. Rupecht. Sigrid. Vanecek. Hans. Wagner. Joachim. Joachim. Wagner. Sigrid. Ruprecht. Peter. Merlet. Peter. Kuhn.
2. Johnson. Frederic A.. Colburn. Charles B.. The Tetrafluorohydrazine-Difluoroamino Radical Equilibrium. Journal of the American Chemical Society. July 1961. 83. 14. 3043–3047. 10.1021/ja01475a018.
3. Brown. R. D.. Burden. F. R.. Hart. B. T.. Williams. G. R.. The electronic structure of the NF₂ radical. Theoretica Chimica Acta. 1973. 28. 4. 339–353. 10.1007/BF00529015. 100649705.
4. 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. 10.1021/ic50048a024. molecule dimensions and angles
5. Web site: Nitrogen difluoride NF₂(g).
6. Brown. R.D.. Burden. F.R.. Godfrey. P.D.. Gillard. I.R.. Microwave spectrum of NF₂. Journal of Molecular Spectroscopy. August 1974. 52. 2. 301–321. 10.1016/0022-2852(74)90121-0. 1974JMoSp..52..301B.
7. Trainor. Daniel W.. Electron dissociative attachment to nitrogen difluoride radicals. The Journal of Physical Chemistry. February 1989. 93. 3. 1134–1136. 10.1021/j100340a022.