Hydrazinium

Structures of two protonated derivatives of hydrazine: N2H6+ and N2H62+.

Hydrazinium is the cation with the formula N2H5+. In some cases, "hydrazine" implies N2H5+, e.g. the salt hydrazinium sulfate. Hydrazinium is derived from hydrazine by protonation (treatment with a strong acid). Salts of hydrazinium are common reagents in chemistry and are often used in certain industrial processes. Both are water-soluble, colorless salts.[1] Hydrazinium is a weak acid with pKa = 8.1.

Hydrazinium azide

One of the most unusual (and more unstable) salts of hydrazinium is the azide. Hydrazine azide (N5H5), the salt of hydrazine and hydrazoic acid, was of scientific interest, because of its high nitrogen content and explosive properties. Structurally, it is [N
2H
5]+
[N
3]−
.[2] It decomposes explosively into hydrazine, ammonia and nitrogen gas:[3]

12 N
5H
5 → 3 N
2H
4 + 16 NH
3 + 19 N
2

Hydrazinediium

Hydrazinium may itself be protonated to give a dication known as hydrazinediium or hydrazinium(2+); with the formula N2H62+. Reaction of hydrazinium azide with sulfuric acid gives quantitative yields of pure hydrazinediium sulfate and hydrazoic acid:[4]

[N2H5+][N3-] + H2SO4 → [N2H62+][SO42-] + HN3

Hydrazinediium adopts an ethane-like structure.

References

  1. ↑ Jean-Pierre Schirmann, Paul Bourdauducq "Hydrazine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a13_177.
  2. ↑ Chiglien, G.; Etienne, J.; Jaulmes, S.; Laruelle, P. (15 September 1974). "Structure cristalline de l'azoture d'hydrazinium, N5H5". Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry 30 (9): 2229–2233. doi:10.1107/S0567740874006790.
  3. ↑ G. B. Manelis (2003). Thermal decomposition and combustion of explosives and propellants. CRC Press. p. 235. ISBN 0-415-29984-5.
  4. ↑ Klapötke, T.; Peter S. White; Inis C. Tornieporth-Oetting (1996). "Reaction of hydrazinium azide with sulfuric acid: the X-ray structure of [N
    2    H
    6    ][SO
    4    ]    ". Polyhedron 15 (15): 2579–2582. doi:10.1016/0277-5387(95)00527-7.
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