Cyclooctadeca-1,3,5,7,9,11,13,15,17-nonayne or cyclo 8arbon is an

allotrope of carbon Carbon is capable of forming many allotropes (structurally different forms of the same element) due to its valency. Well-known forms of carbon include diamond and graphite. In recent decades, many more allotropes have been discovered and rese ...

with

molecular 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 symbols, ...

. The molecule is a

ring Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...

of eighteen

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 ...

atoms, connected by alternating

triple Triple is used in several contexts to mean "threefold" or a " treble": Sports * Triple (baseball), a three-base hit * A basketball three-point field goal * A figure skating jump with three rotations * In bowling terms, three strikes in a row * ...

and single bonds; thus, it is a polyyne and a

cyclocarbon In organic chemistry, a cyclo 'n''arbon (or simply cyclocarbon) is a chemical compound consisting solely of a number ''n'' of carbon atoms covalently linked in a ring. Since the compounds are composed only of carbon atoms, they are allotropes of ...

. Cyclo 8arbon is the smallest cyclo 'n''arbon predicted to be thermodynamically stable, with a computed

strain energy In physics, the elastic potential energy gained by a wire during elongation with a tensile (stretching) force is called strain energy. For linearly elastic materials, strain energy is: : U = \frac 1 2 V \sigma \epsilon = \frac 1 2 V E \epsilon ...

of 72 kilocalories per mole. Above 122K, it explosively decomposes to amorphous

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...

. A collaboration of teams at IBM and the

University of Oxford , mottoeng = The Lord is my light , established = , endowment = £6.1 billion (including colleges) (2019) , budget = £2.145 billion (2019–20) , chancellor ...

team claimed to synthesize it in solid state in 2019 by

electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outc ...

decarbonylation Decarbonylation is a type of organic reaction that involves loss of CO. It is often an undesirable reaction since it represents a degradation. In the chemistry of metal carbonyls, decarbonylation describes a substitution process, whereby a CO lig ...

of several sites of a cyclobutanone structure: Later, researchers from Spain have used computational techniques to probe the structural and electronic properties of the molecule, and have discovered it to be an electron acceptor. Synthese C18

According to these IBM researchers, the

electronic structure In quantum chemistry, electronic structure is the state of motion of electrons in an electrostatic field created by stationary nuclei. The term encompasses both the wave functions of the electrons and the energies associated with them. Electr ...

of their product consists of alternating

triple bond A triple bond in chemistry is a chemical bond between two atoms involving six bonding electrons instead of the usual two in a covalent single bond. Triple bonds are stronger than the equivalent single bonds or double bonds, with a bond order o ...

s and single bonds, rather than a

cumulene In organic chemistry, a cumulene is a compound having three or more ''cumulative'' (consecutive) double bonds. They are analogous to allenes, only having a more extensive chain. The simplest molecule in this class is butatriene (), which is al ...

-type structure of consecutive

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...

s. This supposedly makes this molecule a

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

References

{{Allotropes of carbon Aromatic compounds Group IV semiconductors Polyynes Cyclocarbons Substances discovered in the 2010s