Hexazine

Hexazine (also known as hexaazabenzene) is a hypothetical allotrope of nitrogen composed of 6 nitrogen atoms arranged in a ring-like structure analogous to that of benzene. As a neutrally charged species, it would be the final member of the azabenzene (azine) series, in which all of the methine groups of the benzene molecule have been replaced with nitrogen atoms. The two last members of this series, hexazine and pentazine, have not been observed, although all other members of the azine series have (such as pyridine, pyrimidine, pyridazine, pyrazine, triazines, and tetrazines).

Hexazine

Names
Preferred IUPAC name Hexazine (preselected name)
Systematic IUPAC name Hexaazabenzene
Other names Hexazabenzene[1] Hexaazabenzene Azabenzene
Identifiers
CAS Number	7616-35-5 N
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:36869 N
ChemSpider	10140271 N
Gmelin Reference	1819
PubChem CID	[https://pubchem.ncbi.nlm.nih.gov/compound/correct pubchem from PubChem 11966278 pubchem from PubChem]
CompTox Dashboard (EPA)	DTXSID50474898
InChI InChI=1S/N6/c1-2-4-6-5-3-1 N Key: YRBKSJIXFZPPGF-UHFFFAOYSA-N N
SMILES n1nnnnn1 N1=NN=NN=N1
Properties
Chemical formula	N6
Molar mass	84.042 g·mol−1
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

While a neutrally charged hexazine species has not yet been synthesized, two negatively charged variants, [N₆]^2-[2] and [N₆]^4-,^[3] have been produced in potassium-nitrogen compounds under very high pressures (> 40 GPa) and temperatures (> 2000 K). In particular, [N₆]^4- is aromatic, respecting Hückel's rule, while [N₆]^2- is anti-aromatic.

Stability

The hexazine molecule bears a structural similarity to the very stable benzene molecule. Like benzene, it has been calculated that hexazine is likely an aromatic molecule. Despite this, it has yet to be synthesized. Additionally, it has been predicted computationally that the hexazine molecule is highly unstable, possibly due to the lone pairs on the nitrogen atoms, which may repel each other electrostatically and/or cause electron-donation to sigma antibonding orbitals. A figure-8-shaped isomer is predicted to be metastable.^[4]

See also

• 6-membered rings with other numbers of nitrogen atoms: pyridines, diazines, triazines, tetrazines, and (like hexazine, theoretical) pentazines
• Azide
• Pentazole (HN₅)
• Other molecular allotropes of nitrogen: tetranitrogen (N₄), octaazacubane (N₈)
• Other inorganic benzene analogues: borazine, hexaphosphabenzene

References

1. "Hexazine - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
2. Wang, Yu; Bykov, Maxim; Chepkasov, Ilya; Samtsevich, Artem; Bykova, Elena; Zhang, Xiao; Jiang, Shu-qing; Greenberg, Eran; Chariton, Stella; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F. (July 2022). "Stabilization of hexazine rings in potassium polynitride at high pressure". Nature Chemistry. 14 (7): 794–800. arXiv:2010.15995. Bibcode:2022NatCh..14..794W. doi:10.1038/s41557-022-00925-0. ISSN 1755-4330. PMID 35449217. S2CID 226222305.
3. Laniel, Dominique; Trybel, Florian; Yin, Yuqing; Fedotenko, Timofey; Khandarkhaeva, Saiana; Aslandukov, Andrey; Aprilis, Georgios; Abrikosov, Alexei I.; Bin Masood, Talha; Giacobbe, Carlotta; Bright, Eleanor Lawrence; Glazyrin, Konstantin; Hanfland, Michael; Wright, Jonathan; Hotz, Ingrid (2023-03-06). "Aromatic hexazine [N6]4− anion featured in the complex structure of the high-pressure potassium nitrogen compound K9N56". Nature Chemistry. 15 (5): 641–646. Bibcode:2023NatCh..15..641L. doi:10.1038/s41557-023-01148-7. ISSN 1755-4349. PMID 36879075. S2CID 257377020.
4. J. Fabian and E. Lewars (2004). "Azabenzenes (azines) — The nitrogen derivatives of benzene with one to six N atoms: Stability, homodesmotic stabilization energy, electron distribution, and magnetic ring current; a computational study" (PDF). Canadian Journal of Chemistry. 82 (1): 50–69. doi:10.1139/v03-178. Archived from the original (PDF) on 2005-03-29.

Further reading

• P. Saxe and H. F. Schaefer III (1983). "Cyclic D_6h Hexaazabenzene-A Relative Minimum on the N₆ Potential Energy Hypersurface?". Journal of the American Chemical Society. 105 (7): 1760–1764. doi:10.1021/ja00345a010.
• H. Huber (1982). "Is Hexazine Stable?". Angewandte Chemie International Edition. 21 (1): 64–65. doi:10.1002/anie.198200641.
• M. N. Glukhovtsev and P. von Ragué Schleyer (1992). "Structures, bonding and energies of N[6] isomers". Chemical Physics Letters. 198 (6): 547–554. Bibcode:1992CPL...198..547G. doi:10.1016/0009-2614(92)85029-A.
• T.-K. Ha, R. Cimiraglia and M.T. Nguyen (1981). "Can hexazine (N6) be stable?". Chemical Physics Letters. 83 (2): 317–319. Bibcode:1981CPL....83..317H. doi:10.1016/0009-2614(81)85471-1.

External links

• Media related to Hexazine at Wikimedia Commons