Hexazine is a hypothetical allotrope of nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 composed of 6 nitrogen atoms arranged in a ring-like structure analogous to that of benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

. It would be the final member of the azabenzene (azine) series, having all of the methylidyne

Methylidyne

Methylidyne is a carbyne encountered in organic chemistry. Methylidyne has a linear doublet ground state and is thus paramagnetic. It is stable in the gaseous state. Methylidyne can be considered to be a monoradical; addition reactions are very fast and exothermic. Methylidyne tends to polymerise...

 groups of the benzene molecule 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

Pyridine

Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

, pyrimidine

Pyrimidine

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring...

, pyridazine

Pyridazine

Pyridazine is a heteroaromatic organic compound with the molecular formula C4H4N2, sometimes called 1,2-diazine. It contains a six-membered ring with two adjacent nitrogen atoms. It is a colorless liquid with a boiling point of 208 °C....

, pyrazine

Pyrazine

Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2.Pyrazine is a symmetrical molecule with point group D2h. Derivatives like phenazine are well known for their antitumor, antibiotic and diuretic activity. Pyrazine is less basic in nature than pyridine, pyridazine...

, 1,3,5-triazine

1,3,5-Triazine

1,3,5-triazine, also called s-triazine, is an organic chemical compound with the formula 3. It is a six-membered heterocyclic aromatic ring, one of several isomeric triazines. S-triazine and its derivatives are useful in a variety of applications.-Use in organic chemistry:As a reagent in organic...

 and tetrazine

Tetrazine

Tetrazine is an unstable compound that consists of a six-membered aromatic ring containing four nitrogen atoms with the molecular formula C2H2N4. The name tetrazine is used in the nomenclature of derivatives of this compound...

).

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. In fact, it has been predicted computationally that the hexazine molecule is highly unstable. It has been suggested that this predicted instability is caused by the lone pair

Lone pair

In chemistry, a lone pair is a valence electron pair without bonding or sharing with other atoms. They are found in the outermost electron shell of an atom, so lone pairs are a subset of a molecule's valence electrons...

s on the nitrogen atoms, which may repel each other electrostatically and/or cause electron-donation to sigma antibonding

Antibonding

Antibonding is a type of chemical bonding. An antibonding orbital is a form of molecular orbital that is located outside the region of two distinct nuclei...

 orbitals

Molecular orbital

In chemistry, a molecular orbital is a mathematical function describing the wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of finding an electron in any specific region. The term "orbital" was first...

.

See also

• Azide
  Azide
  Azide is the anion with the formula N3−. It is the conjugate base of hydrazoic acid. N3− is a linear anion that is isoelectronic with CO2 and N2O. Per valence bond theory, azide can be described by several resonance structures, an important one being N−=N+=N−...
  
  
• Octaazacubane
  Octaazacubane
  Octaazacubane is a hypothetical allotrope of nitrogen, whose molecules have eight atoms arranged into a cube. It can be regarded as a derivative of cubane, where all eight carbon atoms have been replaced with a nitrogen atom...
  
   (Nitrogen allotrope with formula N₈)
• Pentazole
  Pentazole
  Pentazole is an aromatic chemical molecule consisting of a five-membered ring with all nitrogen atoms, one of which is bonded to a hydrogen atom. It has a molecular formula of HN5. Its SMILES structure is...
  
  
• Tetranitrogen
  Tetranitrogen
  As reported in the January 18, 2002 edition of Science at the Sapienza University of Rome, Fulvio Cacace and his colleagues created a new nitrogen molecule known as tetranitrogen, with the structure N4...
  
  (Nitrogen allotrope with formula N₄)