The tetraoxygen molecule (O
4), also called oxozone, is an
allotrope
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical State of matter, state, known as allotropes of the elements. Allotropes are different structural modifications o ...
of
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
consisting of four oxygen atoms.
History
Tetraoxygen was first predicted in 1924 by
Gilbert N. Lewis
Gilbert Newton Lewis (October 23 or October 25, 1875 – March 23, 1946) was an American physical chemist and a Dean of the College of Chemistry at University of California, Berkeley. Lewis was best known for his discovery of the covalent bond a ...
, who proposed it as an explanation for the failure of
liquid oxygen
Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an app ...
to obey
Curie's law
For many paramagnetic materials, the magnetization of the material is directly proportional to an applied magnetic field, for sufficiently high temperatures and small fields. However, if the material is heated, this proportionality is reduced. For ...
. Though not entirely inaccurate, computer simulations indicate that although there are no stable O
4 molecules in liquid oxygen, O
2 molecules do tend to associate in pairs with antiparallel
spin
Spin or spinning most often refers to:
* Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning
* Spin, the rotation of an object around a central axis
* Spin (propaganda), an intentionally ...
s, forming transient O
4 units. In 1999, researchers thought that
solid oxygen in its ε-phase, also known as red oxygen, (at pressures above 10
GPa) was O
4.
However, in 2006, it was shown by
X-ray crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
that this stable
phase is in fact
octaoxygen
Octaoxygen, also known as boxygen, is an allotrope of oxygen consisting of eight oxygen atoms, also known as ε-oxygen or red oxygen. This allotrope forms above at pressures greater than 17 GPa.
Preparation and properties
As the pressure of o ...
(). Nevertheless, positively charged tetraoxygen has been detected as a short-lived
chemical species
A chemical species is a chemical substance or ensemble composed of chemically identical molecular entities that can explore the same set of molecular energy levels on a characteristic or delineated time scale. These energy levels determine the wa ...
in
mass spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is u ...
experiments.
[
]
Structure
Theoretical calculations have predicted the existence of
metastable
In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy.
A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...
O
4 molecules with two different shapes: a "puckered" square like
cyclobutane
Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colourless gas and commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes. Cyclobutane itself is of no commerci ...
or
S4, and a "pinwheel" with three oxygen atoms surrounding a central one in a
trigonal planar
In chemistry, trigonal planar is a molecular geometry model with one atom at the center and three atoms at the corners of an equilateral triangle, called peripheral atoms, all in one plane. In an ideal trigonal planar species, all three ligands ...
formation similar to
boron trifluoride
Boron trifluoride is the inorganic compound with the formula BF3. This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.
Structure and bond ...
. It was previously pointed out that the "pinwheel" O
4 molecule should be the natural continuation of the
isoelectronic
Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in th ...
series
,
,
,
[Jubert,A.H.; E.L.Varetti (1986). "On the possible existence of the O4 molecule with D3h symmetry". Anales de Química (Spain)82:227-230.] and analogous to
SO3; that observation served as the basis for the mentioned theoretical calculations.
In 2001, a team at the
University of Rome La Sapienza
The Sapienza University of Rome ( it, Sapienza – Università di Roma), also called simply Sapienza or the University of Rome, and formally the Università degli Studi di Roma "La Sapienza", is a public research university located in Rome, Ita ...
conducted a
neutralization-reionization mass spectrometry experiment to investigate the structure of free O
4 molecules.
Their results did not agree with either of the two proposed molecular structures, but they did agree with a
complex
Complex commonly refers to:
* Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe
** Complex system, a system composed of many components which may interact with each ...
between two O
2 molecules, one in the
ground state
The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. ...
and the other in a specific
excited state
In quantum mechanics, an excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum). Excitation refers to ...
.
Absorption bands
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identi ...
of O
4 e.g. at 360, 477 and 577 nm are frequently used to achieve
aerosol inversions in atmospheric optical
absorption spectroscopy
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating fi ...
. Due to the known distribution of O
2 and therefore also O
4, O
4 slant column densities can be used to retrieve
aerosol
An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of anthropogen ...
profiles which can then be used again in
radiative transfer models to model light paths.
[
]
See also
*
Tetranitrogen (N
4)
*
Solid oxygen
*
Liquid oxygen
Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an app ...
References
{{oxygenallotropes
Allotropes of oxygen
2001 in science
de:Allotrope Formen von Sauerstoff#Tetrasauerstoff