Tricarbon (systematically named 1λ
2,3λ
2-propadiene and ''catena''-tricarbon) is an
inorganic compound with the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbol ...
(also written
(μ-C)Cor ). It is a colourless gas that only persists in dilution or solution as an
adduct
An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
. It is one of the simplest
unsaturated carbene
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.
The term "carbene" ma ...
s. Tricarbon can be found in interstellar space and can be produced in the laboratory by a process called
laser ablation.
Natural occurrence
Tricarbon is a small
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
cluster first
spectroscopically observed in the early 20th century in the tail of a comet by
William Huggins
Sir William Huggins (7 February 1824 – 12 May 1910) was an English astronomer best known for his pioneering work in astronomical spectroscopy together with his wife, Margaret.
Biography
William Huggins was born at Cornhill, Middlesex, in ...
and subsequently identified in
stellar atmosphere
The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone.
Overview
The stellar atmosphere is divided into several regions of distinct character:
* The photosphere, whi ...
s. Small carbon clusters like tricarbon and
dicarbon are regarded as soot precursors and are implicated in the formation of certain industrial
diamond
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...
s and in the formation of
fullerene
A fullerene is an allotrope of carbon whose molecule consists of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms. The molecule may be a hollow sphere, ...
s.
C
3 has also been identified as a transient species in various
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
reactions.
Properties
Chemical properties
The chemical properties of C
3 was investigated in the 1960s by Professor Emeritus
Philip S. Skell of
Pennsylvania State University, who showed that certain reactions of carbon vapor indicated its generation, such as the reaction with isobutylene to produce 1,1,1',1'-tetramethyl-bis-ethanoallene.
Physical properties
The ground state
molecular geometry
Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that dete ...
of tricarbon has been identified as linear via its characteristic symmetric and antisymmetric stretching and bending vibrational modes and bears
bond length
In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest of ...
s of 129 to 130
picometer
The picometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: pm) or picometer (American spelling) is a unit of length in the International System of Units (SI), equal to , or one trillionth of ...
corresponding to those of
alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
s. The
ionization potential
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
is determined experimentally at 11 to 13.5
electronvolt
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacuum ...
s.
In contrast to the linear tricarbon molecule, the
cation is bent.
Nomenclature
The systematic names ''1λ
2,3λ
2-propadiene'', and ''μ-carbidodicarbon'', valid
IUPAC
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
names, are constructed according to the substitutive and additive nomenclatures, respectively.
In appropriate contexts, tricarbon can be viewed as
propadiene
Propadiene () or allene () is the organic compound with the formula . It is the simplest allene, i.e. a compound with two adjacent carbon double bonds. As a constituent of MAPP gas, it has been used as a fuel for specialized welding.
Production ...
with four hydrogen atoms removed, or as propane with eight hydrogen atoms removed; and as such, ''propadienediylidene'' or ''propanetetraylidene'', respectively, may be used as a context-specific systematic names, according to substitutive nomenclature. By default, these names pay no regard to the radicality of the tricarbon molecule. In even more specific context, these can also name the non-radical singlet state, whereas the diradical state is named ''propadienediylylidene'', or ''propanediyldiylidene'', and the tetraradical state is named ''propedienetetrayl'' or ''propanetetraylylidene''.
[Skell, P. S.; Wescott, L. D. (1963)]
See also
*
Hydrocarbons
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or e ...
*
Alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
s
*
List of molecules in interstellar space
This is a list of molecules that have been detected in the interstellar medium and circumstellar envelopes, grouped by the number of component atoms. The chemical formula is listed for each detected compound, along with any ionized form that has a ...
*
Cyclopropatriene
Cyclopropatriene is a hypothetical compound () which is an allotrope of carbon. It was once proposed as a candidate for a spectroscopically observed tricarbon species. It is a cyclic cumulene
In organic chemistry, a cumulene is a compound h ...
References
Further reading
*
*
{{Molecules detected in outer space
Astrochemistry
Allotropes of carbon
Homonuclear triatomic molecules