Pentazole
Encyclopedia
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 . 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
, triazole
s, tetrazole
s, and pentazole. One can consider pentazole to be at the interface between inorganic
and organic chemistry
.
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.
cation (N5+) is known. The mass spectrometer signal for the pentazolide anion (N5-) has been detected from the decomposition of substituted phenyl pentazoles. There was a first report of the synthesis of pentazole and pentazole anion in solution as evidenced by their 15N isotope labeled azide
product, but the evidence for the formation of pentazole anion was disputed. Later experiments that involved the detailed analysis of decomposition products demonstrated the generation of pentazole. The experimental conclusions were supported by high level theoretical
calculations. However, pentazole 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, which should be highly potent propellant
s for space travel
.
Azole
An azole is a class of five-membered nitrogen heterocyclic ring compounds containing at least one other non-carbon atom of either nitrogen, sulfur, or oxygen. The parent compounds are aromatic and have two double bonds; there are successively reduced analogs with fewer...
compounds containing one to five nitrogen atoms. This set contains pyrrole
Pyrrole
Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH. It is a colourless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3...
, imidazole
Imidazole
Imidazole is an organic compound with the formula C3H4N2. This aromatic heterocyclic is a diazole and is classified as an alkaloid. Imidazole refers to the parent compound, whereas imidazoles are a class of heterocycles with similar ring structure, but varying substituents...
, pyrazole
Pyrazole
Pyrazole refers both to the class of simple aromatic ring organic compounds of the heterocyclic diazole series characterized by a 5-membered ring structure composed of three carbon atoms and two nitrogen atoms in adjacent positions, and to the unsubstituted parent compound...
, triazole
Triazole
Triazole refers to either one of a pair of isomeric chemical compounds with molecular formula C2H3N3, having a five-membered ring of two carbon atoms and three nitrogen atoms.The two isomers are:*1,2,3-Triazole 100px*1,2,4-Triazole 100px...
s, tetrazole
Tetrazole
Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen and one carbon atom . The simplest is tetrazole itself, CN4H2. They are unknown in nature...
s, and pentazole. One can consider pentazole to be at the interface between inorganic
Inorganic chemistry
Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...
and organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
.
Derivative
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 phenyl pentazole, where the pentazole ring is highly stabilized by conjugationConjugated system
In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the...
with the phenyl ring. The derivative 4-dimethylaminophenylpentazole
4-Dimethylaminophenylpentazole
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...
is among the most stable pentazole compounds known, although it still decomposes at temperatures over 50°C. It is known that electron-donating groups
Polar effect
The Polar effect or electronic effect in chemistry is the effect exerted by a substituent on modifying electrostatic forces operating on a nearby reaction center...
stabilize aryl
Aryl
In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....
pentazole compounds.
Cation
The cyclic pentazolium cation (N5+) is not known due to its probable antiaromatic character; whereas the open chained pentazeniumPentazenium
The pentazenium cation is a positively charged homoleptic polynitrogen ion of the chemical formula . Together with dinitrogen and azide anion, it is one of the only three polynitrogen species obtained in bulk quantities....
cation (N5+) is known. The mass spectrometer signal for the pentazolide anion (N5-) has been detected from the decomposition of substituted phenyl pentazoles. There was a first report of the synthesis of pentazole and pentazole anion in solution as evidenced by their 15N isotope labeled 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−...
product, but the evidence for the formation of pentazole anion was disputed. Later experiments that involved the detailed analysis of decomposition products demonstrated the generation of pentazole. The experimental conclusions were supported by high level theoretical
Theoretical chemistry
Theoretical chemistry seeks to provide theories that explain chemical observations. Often, it uses mathematical and computational methods that, at times, require advanced knowledge. Quantum chemistry, the application of quantum mechanics to the understanding of valency, is a major component of...
calculations. However, pentazole 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, which should be highly potent propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
s for space travel
Spaceflight
Spaceflight is the act of travelling into or through outer space. Spaceflight can occur with spacecraft which may, or may not, have humans on board. Examples of human spaceflight include the Russian Soyuz program, the U.S. Space shuttle program, as well as the ongoing International Space Station...
.