organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

, a carbyne is a general term for any compound whose

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

consists of an

electrically neutral Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other an ...

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

atom connected by a single covalent bond and has three non-bonded electrons. The carbon atom has either one or three unpaired

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s, depending on its excitation state; making it a radical. The

chemical formula 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 symbols, such as pare ...

can be written or (also written as ), or just CH. Carbynes can be seen as derivatives of the simplest such compound, the methylidyne radical or unsubstituted carbyne or , in which the functional group is a

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

atom. Reported for the first time back in 1967 by Kasatochkin, carbyne is an infinite sp1 hybridized long linear chain of carbon, where each link is just a single carbon atom.

Electronic configuration

Carbyne molecules are generally found to be in electronic

doublet state In quantum mechanics, a doublet is a composite quantum state of a system with an effective spin of 1/2, such that there are two allowed values of the spin component, −1/2 and +1/2. Quantum systems with two possible states are sometimes called ...

s: the non-bonding electrons on carbon are arranged as one radical (unpaired electron) and one electron pair, leaving a vacant

atomic orbital In quantum mechanics, an atomic orbital () is a Function (mathematics), function describing the location and Matter wave, wave-like behavior of an electron in an atom. This function describes an electron's Charge density, charge distribution a ...

, rather than being a triradical (the quartet state). The simplest case is the CH radical, which has an

electron configuration In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon ato ...

. Here the 1σ

molecular orbital In chemistry, a molecular orbital is a mathematical function describing the location and 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 ...

is essentially the carbon 1s atomic orbital, and the 2σ is the C–H bonding orbital formed by overlap of a carbon sp

hybrid orbital Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two diff ...

with the hydrogen 1s orbital. The 3σ is a carbon non-bonding orbital pointing along the C–H axis away from the hydrogen, while there are two non-bonding 1π orbitals perpendicular to the C–H axis. However the 3σ is an sp hybrid which has lower energy than the 1π orbital which is pure p, so the 3σ is filled before the 1π. The CH radical is in fact

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 ...

with the nitrogen atom which does have three unpaired electrons in accordance with Hund's rule of maximum multiplicity. However the nitrogen atom has three degenerate p orbitals, in contrast to the CH radical where hybridization of one orbital (the 3σ) leads to an energy difference.

Occurrence

A carbyne can occur as a short-lived reactive intermediate. For instance, fluoromethylidyne (CF) can be detected in the gas phase by spectroscopy as an intermediate in the flash photolysis of CHFBr₂. Carbynes can act as trivalent

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s in complexes with transition metals, in which they are connected to a

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

by the three non-bonded electrons in the –C^3• group. Examples of such

coordination compound A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...

s are , W Br( CO)₂( 2,2'-bipyridine)≡ C-

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...

and WBr(CO)₂( PPh₃)₂≡C-NR₂. Such a compound can be obtained by the reaction of

tungsten hexacarbonyl Tungsten hexacarbonyl (also called tungsten carbonyl) is an organometallic compound with the formula W(CO)6. This complex gave rise to the first example of a dihydrogen complex.Kubas, G. J., Metal Dihydrogen and σ-Bond Complexes, Kluwer Academic ...

W(CO)₆ with lithium diisopropylamide to form ( ⁱPr₂N)(OLi)C=W(CO)₅. This salt is then oxidized with either oxalyl bromide or triphenylphosphine dibromide, followed by addition of triphenylphosphine. Another method is to treat a methoxy metal

carbene In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a Valence (chemistry), valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms. Th ...

with a

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

References

{{Authority control Free radicals Organometallic chemistry