Pentazole

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Pentazole
Kekule, skeletal formula of pentazole Pentazole.png
Kekulé, skeletal formula of pentazole
Ball-and-stick 3D structure Pentazole-3D-balls.png
Ball-and-stick 3D structure
Names
Systematic IUPAC name
1H-Pentazole [1]
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/HN5/c1-2-4-5-3-1/h(H,1,2,3,4,5) Yes check.svgY
    Key: WUHLVXDDBHWHLQ-UHFFFAOYSA-N Yes check.svgY
  • n1nn[nH]n1
  • N1N=NN=N1
Properties
N
5
H
Molar mass 71.0414 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Pentazole is an aromatic molecule consisting of a five-membered ring with all nitrogen atoms, one of which is bonded to a hydrogen atom. It has the molecular formula HN5. Although strictly speaking a homocyclic, inorganic compound, pentazole has historically been classed as the last in a series of heterocyclic azole compounds containing one to five nitrogen atoms. This set contains pyrrole, imidazole, pyrazole, triazoles, tetrazole, and pentazole.

Contents

Derivatives

Substituted analogs of pentazole are collectively known as pentazoles. As a class, they are unstable and often highly explosive compounds. The first pentazole synthesized was phenylpentazole, where the pentazole ring is highly stabilized by conjugation with the phenyl ring. The derivative 4-dimethylaminophenylpentazole is among the most stable pentazole compounds known, although it still decomposes at temperatures over 50 °C. It is known that electron-donating groups stabilize aryl pentazole compounds. [2]

Ions

The cyclic pentazolium cation (N+
5
) is not known due to its probable antiaromatic character; whereas the open-chained pentazenium cation (N+
5
) is known. Butler et al. first demonstrated the presence of the cyclic N
5
in solution through the decomposition of substituted aryl pentazoles at low temperature. The presence of N
5
H
and N
5
(held in solution through the interaction with zinc ions) was proven primarily using 15N NMR techniques of the decomposition products. [3] These results were initially challenged by some authors, [4] but subsequent experiments involving the detailed analysis of the decomposition products, complemented by computational studies, bore out the initial conclusion. [5] [6] [7] The pentazolide anion is not expected to last longer than a few seconds in aqueous solution without the aid of complexing agents. The discovery of pentazoles spurred attempts to create all-nitrogen salts such as N+
5
N
5
, which should be highly potent propellants for space travel.

In 2002, the pentazolate anion was first detected with electrospray ionization mass spectrometry [8] In 2016, the ion was also detected in solution. [9] In 2017, white cubic crystals of the pentazolate salt, (N5)6(H3O)3(NH4)4Cl were announced. In this salt, the N
5
rings are planar. The bond lengths in the ring are 1.309 Å, 1.310 Å, 1.310 Å, 1.324 Å, and 1.324 Å. [10] When heated, the salt is stable up to 117 °C, and over this temperature it decomposes to ammonium azide. [10] Under extreme pressure conditions, the pentazolate ion was also synthesized. It was first obtained in 2016 in the form of the CsN5 salt by compressing and laser-heating a mixture of CsN3 embedded in molecular N2 at 60 GPa. Following the pressure release, it was found metastable down to 18 GPa. [11] In 2018, another team reported the high pressure synthesis of LiN5 above 45 GPa from a pure lithium surrounded by molecular nitrogen. This compound could be retained down to ambient conditions after the complete release of pressure. [12]

Related Research Articles

In chemistry, azide is a linear, polyatomic anion with the formula N−3 and structure N=N+=N. It is the conjugate base of hydrazoic acid HN3. Organic azides are organic compounds with the formula RN3, containing the azide functional group. The dominant application of azides is as a propellant in air bags.

In chemistry, catenation is the bonding of atoms of the same element into a series, called a chain. A chain or a ring shape may be open if its ends are not bonded to each other, or closed if they are bonded in a ring. The words to catenate and catenation reflect the Latin root catena, "chain".

<span class="mw-page-title-main">Imidazole</span> Chemical compound

Imidazole is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-adjacent nitrogen atoms in meta-substitution.

The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups. In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of activating an intermediate in a preceding step. As such, there is no obvious retron for this reaction. The reaction was reported by Nikolai Kischner in 1911 and Ludwig Wolff in 1912,

<span class="mw-page-title-main">Hydrazoic acid</span> Unstable and toxic chemical compound

Hydrazoic acid, also known as hydrogen azide or azoimide, is a compound with the chemical formula HN3. It is a colorless, volatile, and explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, and is therefore a pnictogen hydride. It was first isolated in 1890 by Theodor Curtius. The acid has few applications, but its conjugate base, the azide ion, is useful in specialized processes.

In chemistry, the phosphonium cation describes polyatomic cations with the chemical formula PR+
4
. These cations have tetrahedral structures. The salts are generally colorless or take the color of the anions.

Azoles are a class of five-membered heterocyclic compounds containing a nitrogen atom and at least one other non-carbon atom as part of the ring. Their names originate from the Hantzsch–Widman nomenclature. The parent compounds are aromatic and have two double bonds; there are successively reduced analogs with fewer. One, and only one, lone pair of electrons from each heteroatom in the ring is part of the aromatic bonding in an azole. Names of azoles maintain the prefix upon reduction. The numbering of ring atoms in azoles starts with the heteroatom that is not part of a double bond, and then proceeds towards the other heteroatom.

<span class="mw-page-title-main">Bamford–Stevens reaction</span>

The Bamford–Stevens reaction is a chemical reaction whereby treatment of tosylhydrazones with strong base gives alkenes. It is named for the British chemist William Randall Bamford and the Scottish chemist Thomas Stevens Stevens (1900–2000). The usage of aprotic solvents gives predominantly Z-alkenes, while protic solvent gives a mixture of E- and Z-alkenes. As an alkene-generating transformation, the Bamford–Stevens reaction has broad utility in synthetic methodology and complex molecule synthesis.

<span class="mw-page-title-main">Perbromate</span> Ion

In chemistry, the perbromate ion is the anion having the chemical formula BrO
4
. It is an oxyanion of bromine, the conjugate base of perbromic acid, in which bromine has the oxidation state +7. Unlike its chlorine and iodine analogs, it is difficult to synthesize. It has tetrahedral molecular geometry.

Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound with formula CH2N4, of which three isomers can be formulated.

<span class="mw-page-title-main">Persistent carbene</span> Type of carbene demonstrating particular stability

A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (NHC) (sometimes called Arduengo carbenes), for example diaminocarbenes with the general formula (R2N)2C:, where the four R moieties are typically alkyl and aryl groups. The groups can be linked to give heterocyclic carbenes, such as those derived from imidazole, imidazoline, thiazole or triazole.

<span class="mw-page-title-main">Nitroxyl</span> Chemical compound

Nitroxyl or azanone is the chemical compound HNO. It is well known in the gas phase. Nitroxyl can be formed as a short-lived intermediate in the solution phase. The conjugate base, NO, nitroxide anion, is the reduced form of nitric oxide (NO) and is isoelectronic with dioxygen. The bond dissociation energy of H−NO is 49.5 kcal/mol (207 kJ/mol), which is unusually weak for a bond to the hydrogen atom.

<span class="mw-page-title-main">Ammonium dichromate</span> Chemical compound

Ammonium dichromate is an inorganic compound with the formula (NH4)2Cr2O7. In this compound, as in all chromates and dichromates, chromium is in a +6 oxidation state, commonly known as hexavalent chromium. It is a salt consisting of ammonium ions and dichromate ions.

<span class="mw-page-title-main">Sodium tetraphenylborate</span> Chemical compound

Sodium tetraphenylborate is the organic compound with the formula NaB(C6H5)4. It is a salt, wherein the anion consists of four phenyl rings bonded to boron. This white crystalline solid is used to prepare other tetraphenylborate salts, which are often highly soluble in organic solvents. The compound is used in inorganic and organometallic chemistry as a precipitating agent for potassium, ammonium, rubidium, and cesium ions, and some organic nitrogen compounds.

Cyclodiphosphazanes are saturated four membered P2N2 ring systems and one of the major classes of cyclic phosphazene compounds. Bis(chloro)cyclodiphosphazanes, (cis-[ClP(μ-NR)]2) are important starting compounds for synthesizing a variety of cyclodiphosphazane derivatives by nucleophilic substitution reactions; are prepared by reaction of phosphorus trichloride (PCl3) with a primary amine (RNH2) or amine hydrochlorides (RNH3Cl).

<span class="mw-page-title-main">Pentazenium</span> Polytomic cation (N–N–N–N–N)

In chemistry, the pentazenium cation is a positively-charged polyatomic ion with the chemical formula N+5 and structure N−N−N−N−N. Together with solid nitrogen polymers and the azide anion, it is one of only three poly-nitrogen species obtained in bulk quantities.

<span class="mw-page-title-main">4-Dimethylaminophenylpentazole</span> Chemical compound

4-Dimethylaminophenylpentazole is an unstable, explosive compound that contains the rare pentazole ring, which is composed of five nitrogen atoms. The electron donating effect of the 4-dimethylamino substituent on the phenyl ring makes this compound one of the more stable of the phenylpentazoles. At room temperature, its chemical half-life is only a few hours, although storage is possible at cryogenic temperatures. The compound was first prepared in 1956 along with other substituted phenylpentazoles. Studies have been conducted on various other derivatives, though necessarily limited by the instability of these compounds. Some more highly substituted derivatives, such as 2,6-dihydroxy-4-dimethylaminophenylpentazole, are slightly more stable but conversely, more difficult to make. Current research has focused on forming transition metal complexes of these pentazole derivatives, as the pentazole ring should be stabilised by bonding to the metal centre.

<span class="mw-page-title-main">1,1'-Azobis-1,2,3-triazole</span> Chemical compound

1,1-Azobis-1,2,3-triazole is a moderately explosive but comparatively stable chemical compound which contains a long continuous chain of nitrogen atoms, with an unbroken chain of eight nitrogen atoms cyclised into two 1,2,3-triazole rings. It is stable up to 194 °C. The compound exhibits cis–trans isomerism at the central azo group: the trans isomer is more stable and is yellow, while the cis isomer is less stable and is blue. The two rings are aromatic and form a conjugated system with the azo linkage. This chromophore allows the trans compound to be isomerised to the cis when treated with an appropriate wavelength of ultraviolet light.

<span class="mw-page-title-main">Karl O. Christe</span>

Karl Otto Christe is an inorganic chemist. He is the best reference in respectful handling of a huge number of extremely reactive components and his extensive experience in fluorine chemistry earned him the title of 'The Fluorine God'. His research covers fluorine chemistry of nitrogen and halogens and the synthesis of new energetic materials.

Azidotetrazolate (CN7) is an anion which forms a highly explosive series of salts. The ion is made by removing a proton from 5-azido-1H-tetrazole. The molecular structure contains a five-membered ring with four nitrogen atoms, and an azido side chain connected to the carbon atom. Several salts exist, but they are unstable and spontaneously explode. Rubidium azidotetrazolate was so unstable that it explodes while crystallizing. The potassium and caesium salt also spontaneously explode when dry.

References

  1. "1H-Pentazole - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
  2. Burke, L. A.; Fazen P. J. (Dec 2009). "Correlation Analysis of the Interconversion and Nitrogen Loss Reactions of Aryl Pentazenes and Pentazoles Derived From Aryl Diazonium and Azide Ions". International Journal of Quantum Chemistry. 109 (15): 3613–3618. Bibcode:2009IJQC..109.3613B. doi:10.1002/qua.22408.
  3. Butler, R. N.; Stephens, John C.; Burke, Luke A. (2003). "First generation of pentazole (HN5, pentazolic acid), the final azole, and a zinc pentazolate salt in solution: A new N-dearylation of 1-(p-methoxyphenyl) pyrazoles, a 2-(p-methoxyphenyl) tetrazole and application of the methodology to 1-(p-methoxyphenyl) pentazole". Chemical Communications (8): 1016–1017. doi:10.1039/b301491f. PMID   12744347.
  4. Schroer T, HaigesR, Schneider S, Christe KO (2004-12-31). "The race for the first generation of the pentazolate anion in solution is far from over". Chemical Communications (12): 1607–9. doi:10.1039/B417010E. PMID   15770275.
  5. Butler RN, Hanniffy JM, Stephens JC, Burke LA (2008-01-31). "A Ceric Ammonium Nitrate N-Dearylation of N-p-Anisylazoles Applied to Pyrazole, Triazole, Tetrazole, and Pentazole Rings: Release of Parent Azoles. Generation of Unstable Pentazole, HN5/N5-, in Solution" (PDF). The Journal of Organic Chemistry. 73 (4): 1354–1364. doi:10.1021/jo702423z. PMID   18198892.
  6. Perera SA, Gregusová A, Bartlett RJ (2009-04-01). "First Calculations of 15N−15N J Values and New Calculations of Chemical Shifts for High Nitrogen Systems: A Comment on the Long Search for HN5 and Its Pentazole Anion". The Journal of Physical Chemistry A. 113 (13): 3197–3201. Bibcode:2009JPCA..113.3197P. doi:10.1021/jp809267y. PMID   19271757.
  7. "Galway discovery ahead of the world". The Irish Times. Aug 13, 2009.
  8. Vij, A., Pavlovich, J. G., Wilson, W. W., Vij, V. and Christe, K. O. (2002), Experimental Detection of the Pentaazacyclopentadienide (Pentazolate) Anion, cyclo-N5−. Angew. Chem. Int. Ed., 41: 3051–3054. doi : 10.1002/1521-3773(20020816)41:16<3051::AID-ANIE3051>3.0.CO;2-T
  9. B. Bazanov, U. Geiger, R. Carmieli, D. Grinstein, S. Welner, Y. Haas,Detection of Cyclo-N5− in THF Solution Angew. Chem. Int. Ed. 2016, 55, 13233. doi : 10.1002/anie.201605400
  10. 1 2 Zhang, Chong; Sun, Chengguo; Hu, Bingcheng; Yu, Chuanming; Lu, Ming (26 January 2017). "Synthesis and characterization of the pentazolate anion cyclo-N5ˉ in (N5)6(H3O)3(NH4)4Cl". Science. 355 (6323): 374–376. Bibcode:2017Sci...355..374Z. doi:10.1126/science.aah3840. PMID   28126812. S2CID   206651670.
  11. Steele, Brad A.; Stavrou, Elissaios; Crowhurst, Jonathan C.; Zaug, Joseph M.; Prakapenka, Vitali B.; Oleynik, Ivan I. (2016-12-06). "High-Pressure Synthesis of a Pentazolate Salt". Chemistry of Materials. 29 (2): 735. arXiv: 1612.01918 . doi:10.1021/acs.chemmater.6b04538. ISSN   0897-4756. S2CID   99194135.
  12. Laniel, D.; Weck, G.; Gaiffe, G.; Garbarino, G.; Loubeyre, P. (2018-03-13). "High-Pressure Synthesized Lithium Pentazolate Compound Metastable under Ambient Conditions". The Journal of Physical Chemistry Letters. 9 (7): 1600–1604. doi:10.1021/acs.jpclett.8b00540. ISSN   1948-7185. PMID   29533665.