polyyne

The first reported synthesis of a polyyne was performed in 1869 by {{ill|Carl Andreas Glaser|de|Carl Glaser}}, who observed that copper phenylacetylide ({{chem2|CuC\tC\sC6H5}}) undergoes oxidative dimerization in the presence of air to produce diphenylbutadiyne ({{chem2|C6H5\sC\tC\sC\tC\sC6H5}}).

Interest in these compounds has stimulated research into their preparation by organic synthesis by several general routes. As a main synthetic tool usually acetylene homocoupling reactions like the Glaser coupling or its associated Elinton and Hay protocols are used.{{cite journal |last1=Jevric |first1=Martyn |last2=Nielsen |first2=Mogens Brøndsted |title=Synthetic Strategies for Oligoynes |journal=Asian Journal of Organic Chemistry |date=April 2015 |volume=4 |issue=4 |pages=286–295 |doi=10.1002/ajoc.201402261 }} Moreover, many of such procedures involve a Cadiot–Chodkiewicz coupling or similar reactions to unite two separate alkyne building-blocks or by alkylation of a pre-formed polyyne unit. In addition to that, Fritsch–Buttenberg–Wiechell rearrangement was used as crucial step during the synthesis of the longest known polyyne ({{chem2|C44}}).

{{cite journal |first1=Wesley A. |last1=Chalifoux |first2=Rik R. |last2=Tykwinski |title=Synthesis of polyynes to model the sp-carbon allotrope carbyne |journal=Nature Chemistry |volume=2 |issue=11 |pages=967–971 |date=2010 |doi=10.1038/nchem.828|pmid=20966954 |bibcode=2010NatCh...2..967C |s2cid=24123099 }} An elimination of chlorovinylsilanes was used as a final step in the synthesis of the longest known phenyl end-capped polyynes.{{cite journal |last1=Simpkins |first1=Simon M. E. |last2=Weller |first2=Michael D. |last3=Cox |first3=Liam R. |title=β-Chlorovinylsilanes as masked alkynes in oligoyne assembly: synthesis of the first aryl-end-capped dodecayne |journal=Chemical Communications |date=2007 |issue=39 |pages=4035–7 |doi=10.1039/B707681A|pmid=17912407 }}

Using various techniques, polyynes {{chem2|H(\sC\tC\s)_{n}H}} with n up to 4 or 5 were synthesized during the 1950s. Around 1971, T. R. Johnson and D. R. M. Walton developed the use of end-caps of the form –{{chem2|SiR3}}, where R was usually an ethyl group, to protect the polyyne chain during the chain-doubling reaction using Hay's catalyst (a copper(I)–TMEDA complex).{{cite journal |first1=R. |last1=Eastmond |first2=T.R. |last2=Johnson |first3=D.R.M. |last3=Walton |title=Silylation as a protective method for terminal alkynes in oxidative couplings: A general synthesis of the parent polyynes {{chem|H(C≡C)|n|H}} (n = 4–10, 12) |journal=Tetrahedron |volume=28 |issue=17 |pages=4601–16 |date=1972 |doi=10.1016/0040-4020(72)80041-3}}{{cite journal |first1=T.R. |last1=Johnson |first2=D.R.M. |last2=Walton |title=Silylation as a protective method in acetylene chemistry: Polyyne chain extensions using the reagents, {{chem|Et|3|Si(C≡C)|m|H}} (m = 1, 2, 4) in mixed oxidative couplings |journal=Tetrahedron |volume=28 |issue=20 |pages=5221–36 |date=1972 |doi=10.1016/S0040-4020(01)88941-9}} With that technique they were able to obtain polyynes like {{chem2|(CH3CH2)3Si(\sC\tC\s)_{n}Si(CH2CH3)3}} with n up to 8 in pure state, and with n up to 16 in solution.

Later Tykwinski and co-workers were able to obtain {{chem2|((CH3)2CH)3Si(\sC\tC\s)_{n}Si(CH(CH3)2)3}} polyynes with chain length up to C₂₀.

A polyyne compound with 10 acetylenic units (20 atoms), with the ends capped by Fréchet-type aromatic polyether dendrimers, was isolated and characterized in 2002. Moreover, the synthesis of dicyanopolyynes with up to 8 acetylenic units was reported.{{cite journal |last1=Schermann |first1=Günther |last2=Grösser |first2=Thomas |last3=Hampel |first3=Frank |last4=Hirsch |first4=Andreas |title=Dicyanopolyynes: A Homologous Series of End-Capped Linear sp Carbon |journal=Chemistry – A European Journal |date=1997 |volume=3 |issue=7 |pages=1105–1112 |doi=10.1002/chem.19970030718 |language=en |issn=1521-3765}} The longest phenyl end-capped polyynes were reported by Cox and co-workers in 2007. As of 2010, the polyyne with the longest chain yet isolated had 22 acetylenic units (44 carbon atoms), end-capped with tris(3,5-di-t-butylphenyl)methyl groups.

Alkynes with the formula {{chem2|H(\sC\tC\s)_{n}H}} and n from 2 to 6 can be detected in the decomposition products of partially oxidized copper(I) acetylide ({{chem2|(Cu+)2(-C\tC-)}} (an acetylene derivative known since 1856 or earlier) by hydrochloric acid. A "carbonaceous" residue left by the decomposition also has the spectral signature of {{chem2|(\sC\tC\s)_{n}|}} chains.

{{cite journal |first=Franco |last=Cataldo |title=From dicopper acetylide to carbyne |journal=Polymer International |volume=48 |issue=1 |pages=15–22 |date=1999 |doi=10.1002/(SICI)1097-0126(199901)48:1<15::AID-PI85>3.0.CO;2-# }}

File:Organic polyynes.jpg polyynes]]

Organometallic polyynes capped with metal complexes are well characterized. As of the mid-2010s, the most intense research has concerned rhenium ({{chem2|Re(\sC\tC\s)_{n}Re}}, n = 3–10),{{Cite journal|title = Toward Metal-Capped One-Dimensional Carbon Allotropes: Wirelike C₆−C₂₀ Polyynediyl Chains That Span Two Redox-Active (η⁵-C⁵Me⁵)Re(NO)(PPh³) Endgroups|journal = Journal of the American Chemical Society|date = 2000-02-01|issn = 0002-7863|pages = 810–822|volume = 122|issue = 5|doi = 10.1021/ja992747z|first1 = Roman|last1 = Dembinski|first2 = Tamás|last2 = Bartik|first3 = Berit|last3 = Bartik|first4 = Monika|last4 = Jaeger|first5 = J. A.|last5 = Gladysz}} ruthenium ({{chem2|RuRu(\sC\tC\s)_{n}RuRu}}, n = 4–10),{{Cite journal|title = Diruthenium–Polyyn-diyl–Diruthenium Wires: Electronic Coupling in the Long Distance Regime|journal = Journal of the American Chemical Society|date = 2014-08-27|issn = 0002-7863|pages = 12174–12183|volume = 136|issue = 34|doi = 10.1021/ja507107t|pmid = 25116468|first1 = Zhi|last1 = Cao|first2 = Bin|last2 = Xi|first3 = Diane S.|last3 = Jodoin|first4 = Lei|last4 = Zhang|first5 = Steven P.|last5 = Cummings|first6 = Yang|last6 = Gao|first7 = Sarah F.|last7 = Tyler|first8 = Phillip E.|last8 = Fanwick|first9 = Robert J.|last9 = Crutchley}} iron ({{chem2|Fe(\sC\tC\s)6Fe}}),{{Cite journal|title = Synthesis and Characterization of the Dodecahexaynediyldiiron Complex, Fp*−(C≡C)₆−Fp* [Fp*= Fe(η⁵-C₅Me₅)(CO)2], the Longest Structurally Characterized Polyynediyl Complex|journal = Organometallics|date = 1999-08-01|issn = 0276-7333|pages = 3241–3244|volume = 18|issue = 16|doi = 10.1021/om990266i|first1 = Aizoh|last1 = Sakurai|first2 = Munetaka|last2 = Akita|first3 = Yoshihiko|last3 = Moro-oka}} platinum ({{chem2|Pt(\sC\tC\s)_{n}Pt}}, n = 8–14),{{Cite journal|title = A Synthetic Breakthrough into an Unanticipated Stability Regime: Readily Isolable Complexes in which C₁₆−C₂₈ Polyynediyl Chains Span Two Platinum Atoms|journal = Journal of the American Chemical Society|date = 2005-08-01|issn = 0002-7863|pages = 10508–10509|volume = 127|issue = 30|doi = 10.1021/ja0534598|pmid = 16045336|first1 = Qinglin|last1 = Zheng|first2 = J. A.|last2 = Gladysz}} palladium ({{chem2|Ar(\sC\tC\s)_{n}Pd}}, n = 3–5, Ar = aryl),{{Cite journal|title = Synthesis of Long, Palladium End-Capped Polyynes through the Use of Asymmetric 1-Iodopolyynes|journal = Chemistry: A European Journal|date = 2015-10-22|issn = 1521-3765|pages = 17769–17778|doi = 10.1002/chem.201502737|pmid = 26490174|first1 = Bartłomiej|last1 = Pigulski|first2 = Nurbey|last2 = Gulia|first3 = Sławomir|last3 = Szafert|volume=21|issue = 49}} and cobalt ({{chem2|Co3C(\sC\tC\s)_{n}CCo3}}, n = 7–13){{Cite journal|title = Syntheses and molecular structures of some compounds containing many-atom chains end-capped by tricobalt carbonyl clusters|journal = Journal of Organometallic Chemistry|date = 2008-08-15|pages = 2887–2897|volume = 693|issue = 17|doi = 10.1016/j.jorganchem.2008.06.007|first1 = Michael I.|last1 = Bruce|first2 = Natasha N.|last2 = Zaitseva|first3 = Brian K.|last3 = Nicholson|first4 = Brian W.|last4 = Skelton|first5 = Allan H.|last5 = White}} complexes.

File:Organometallic polyynes.tif polyynes. ]]

Long polyyne chains are said to be inherently unstable in bulk because they can cross-link with each other exothermically.

{{cite web |first=H. |last=Kroto |title=Carbyne and other myths about carbon |date=November 2010 |work=RSC Chemistry World |url=http://www.rsc.org/chemistryworld/Issues/2010/November/CarbyneOtherMythsAboutCarbon.asp}} Explosions are a real hazard in this area of research.{{cite journal |first1=R.H. |last1=Baughman |title=Dangerously Seeking Linear Carbon |journal=Science |volume=312 |pages=1009–1110 |date=2006 |doi=10.1126/science.1125999 |pmid=16709775 |issue=5776|s2cid=93868586 }} They can be fairly stable, even against moisture and oxygen, if the end hydrogen atoms are replaced with a suitably inert end-group, such as tert-butyl or trifluoromethyl. Bulky end-groups, that can keep the chains apart, work especially well at stabilizing polyynes. In 1995 the preparation of carbyne chains with over 300 carbon atoms was reported using this technique.{{cite journal |display-authors=4 |author=Lagow, R.J. |author2=Kampa, J.J. |author3=Han-Chao Wei |author4=Battle, Scott L. |author5=Genge, John W. |author6=Laude, D.A. |author7=Harper, C.J. |author8=Bau, R. |author9=Stevens, R.C. |author10= Haw., J.F. |author11= Munson, E. |title=Synthesis of linear acetylenic carbon: The "sp" carbon allotrope |journal=Science |volume=267 |issue=5196 |pages=362–7 |date=1995 |doi=10.1126/science.267.5196.362 |pmid=17837484|bibcode=1995Sci...267..362L |s2cid=12939062 }} However the report has been contested by a claim that the detected molecules were fullerene-like structures rather than long polyynes.

Polyyne chains have also been stabilised to heating by co-deposition with silver nanoparticles,{{cite journal|last1=Casari|first1=C. S.|last2=Cataldo|first2=F.|display-authors=etal|title=Stabilization of linear carbon structures in a solid Ag nanoparticle assembly|journal=Applied Physics Letters|date=2007|volume=90|issue=1|page=013111|doi=10.1063/1.2430676|arxiv=cond-mat/0610073|bibcode=2007ApPhL..90a3111C|s2cid=119095451}} and by complexation with a mercury-containing tridentate Lewis acid to form layered adducts.{{cite journal|last1=Gabbai|first1=F. P.|last2=Taylor|first2=T. J.|title=Supramolecular Stabilization of α,ω-Diphenylpolyynes by Complexation to the Tridentate Lewis Acid [o-C₆F₄Hg]₃|journal=Organometallics|date=March 24, 2006|volume=25|issue=9|pages=2143–2147|doi=10.1021/om060186w}} Long polyyne chains encapsulated in double-walled carbon nanotubes or in the form of rotaxanes{{cite journal | doi=10.1021/jacs.5b12049 | title=Polyyne Rotaxanes: Stabilization by Encapsulation | year=2016 | last1=Movsisyan | first1=Levon D. | last2=Franz | first2=Michael | last3=Hampel | first3=Frank | last4=Thompson | first4=Amber L. | last5=Tykwinski | first5=Rik R. | last6=Anderson | first6=Harry L. | journal=Journal of the American Chemical Society | volume=138 | issue=4 | pages=1366–1376 | pmid=26752712 | pmc=4772075 }} have also been shown to be stable.{{cite journal|last1=Zhao|first1=C.|last2=Shinohara|first2=H.|title=Growth of Linear Carbon Chains inside Thin Double-Wall Carbon Nanotubes|journal=Journal of Physical Chemistry C|date=2011|volume=115|issue=27|pages=13166–13170|doi=10.1021/jp201647m}} Despite rather low stability of longer polyynes there are some examples of their use as synthetic precursors in organic and organometallic synthesis.{{cite journal |last1=Pigulski |first1=Bartłomiej |last2=Gulia |first2=Nurbey |last3=Szafert |first3=Sławomir |title=Reactivity of Polyynes: Complex Molecules from Simple Carbon Rods |journal=European Journal of Organic Chemistry |issue=7 |pages=1420–1445 |doi=10.1002/ejoc.201801350 |language=en |issn=1099-0690|year=2019 |volume=2019 |s2cid=104400081 }}

Synthetic polyynes of the form {{chem2|R(\sC\tC\s)_{n}R}}, with n about 8 or more, often have a smoothly curved or helical backbone in the crystalline solid state, presumably due to crystal packing effects.{{Cite journal|title = Update 1 of: Carbon in One Dimension: Structural Analysis of the Higher Conjugated Polyynes|journal = Chemical Reviews|date = 2006-11-01|issn = 0009-2665|pages = PR1–PR33|volume = 106|issue = 11|doi = 10.1021/cr068016g|pmid = 17100401|first1 = Slawomir|last1 = Szafert|first2 = J. A.|last2 = Gladysz}} For example, when the cap R is triisopropylsilyl and n is 8, X-ray crystallography of the substance (a crystalline orange/yellow solid) shows the backbone bent by about 25–30 degrees in a broad arch, so that each C−C≡C angle deviates by 3.1 degrees from a straight line. This geometry affords a denser packing, with the bulky cap of an adjacent molecule nested into the concave side of the backbone. As a result, the distance between backbones of neighboring molecules is reduced to about 0.35 to 0.5 nm, near the range at which one expects spontaneous cross-linking. The compound is stable indefinitely at low temperature, but decomposes before melting. In contrast, the homologous molecules with n = 4 or n = 5 have nearly straight backbones that stay at least 0.5 to 0.7 nm apart, and melt without decomposing.{{cite journal |first1=Sara |display-authors=4 |last1=Eisler |first2=Aaron D. |last2=Slepkov |first3=Erin |last3=Elliott |author4=Thanh Luu |first5=Robert |last5=McDonald |first6=Frank A. |last6=Hegmann |first7=Rik R. |last7=Tykwinski |title=Polyynes as a model for carbyne: Synthesis, physical properties, and nonlinear optical response |journal=Journal of the American Chemical Society |volume=127 |issue=8 |pages=2666–76 |date=2005 |doi=10.1021/ja044526l |pmid=15725024}}

A wide range of organisms synthesize polyynes.{{cite journal |author=Minto RE |author2=Blacklock BJ |title=Biosynthesis and function of polyacetylenes and allied natural products |journal=Prog Lipid Res |volume=47 |issue=4 |pages=233–306 |date=July 2008 |pmid=18387369 |pmc=2515280 |doi=10.1016/j.plipres.2008.02.002}}{{cite journal |last=Annabelle |first=L.K. |author2=Shi Shun |last3=Tykwinski |first3=Rik R. |date=2006 |title=Synthesis of Naturally Occurring Polyynes |journal=Angewandte Chemie International Edition |volume=45 |issue=7 |pages=1034–57 |doi=10.1002/anie.200502071 |pmid=16447152 }} These chemicals have various biological activities, including as flavorings and pigments, chemical repellents and toxins, and potential application to biomedical research and pharmaceuticals. In plants, polyynes are found mainly in Asterids clade, especially in the sunflower, carrot, ginseng and bellflower families. However, they can also be found in some members of the tomato, olax, and sandalwood families.{{Cite journal| doi = 10.1007/s11094-014-1159-7| issn = 0091-150X | volume = 48| issue = 9| pages = 613–631| last = Konovalov| first = D. A.| title = Polyacetylene Compounds of Plants of the Asteraceae Family (Review)| journal = Pharmaceutical Chemistry Journal| access-date = 2020-01-07| date = December 2014| s2cid = 41555718| url = http://link.springer.com/10.1007/s11094-014-1159-7| url-access = subscription}} The earliest polyyne to be isolated was dehydromatricaria ester (DME) in 1826; however, it was not fully characterized until later.Stavholt, K., and N. A. Sorensen. 1950. Studies relating to naturally-occurring Acetylene Compounds: V. Dehydro Matricaria Ester (Methyl n-decene-triynoate) from the Essential Oil of Artemisia vulgaris L. Acta Chemica Scandinavia 4.

File:8,10-octadecadiynoic acid.png

The simple fatty acid 8,10-octadecadiynoic acid is isolated from the root bark of the legume Paramacrolobium coeruleum of the family Caesalpiniaceae and has been investigated as a photopolymerizable unit in synthetic phospholipids.{{cite journal |title= Synthesis of photopolymerizable long-chain conjugated diacetylenic acids and alcohols from butadiyne synthons |first1= Zhenchun |last1= Xu |first2= Hoe Sup |last2= Byun |first3= Robert |last3= Bittman |journal= J. Org. Chem. |year= 1991 |volume= 56 |issue= 25 |pages= 7183–7186 |doi= 10.1021/jo00025a045 }}

File:Thiarubrine B.svg]]

Thiarubrine B is the most prevalent among several related light-sensitive pigments that have been isolated from the Giant Ragweed (Ambrosia trifida), a plant used in herbal medicine. The thiarubrines have antibiotic, antiviral, and nematocidal activity, and activity against HIV-1 that is mediated by exposure to light.{{cite journal |title= Total Synthesis of Thiarubrine B [3-(3-Buten-1-ynyl)-6-(1,3-pentadiynyl)-1,2-dithiin], the Antibiotic Principle of Giant Ragweed (Ambrosia trifida) |first1= Eric |last1= Block |first2= Chuangxing |last2= Guo |first3= Mohan |last3= Thiruvazhi |first4= Paul J. |last4= Toscano |journal= J. Am. Chem. Soc. |year= 1994 |volume= 116 |issue= 20 |pages= 9403–9404 |doi= 10.1021/ja00099a097 }}

File:Falcarindiol.svg]]

File:oenanthotoxin-structure.png]]

File:Cicutoxin.svg]]

Polyynes such as falcarindiol can be found in Apiaceae vegetables like carrot, celery, fennel, parsley and parsnip where they show cytotoxic activities.{{cite journal |display-authors=4 |author=Zidorn, C. |author2=Jöhrer, K. |author3=Ganzera, M. |author4=Schubert, B. |author5=Sigmund, E.M. |author6=Mader, J. |author7=Greil, R. |author8=Ellmerer, E.P. |author9=Stuppner, H. |title=Polyacetylenes from the Apiaceae Vegetables Carrot, Celery, Fennel, Parsley, and Parsnip and Their Cytotoxic Activities |journal=J. Agric. Food Chem. |volume=53 |issue=7 |pages=2518–23 |date=2005 |doi=10.1021/jf048041s |pmid=15796588}} Aliphatic {{chem2|C17}}-polyynes of the falcarinol type were described to act as metabolic modulators{{cite journal | last1 = Atanasov | first1 = AG | last2 = Blunder | first2 = M | last3 = Fakhrudin | first3 = N | last4 = Liu | first4 = X | last5 = Noha | first5 = SM | last6 = Malainer | first6 = C | last7 = Kramer | first7 = MP | last8 = Cocic | first8 = A | last9 = Kunert | first9 = O | last10 = Schinkovitz | first10 = A | last11 = Heiss | first11 = EH | last12 = Schuster | first12 = D | last13 = Dirsch | first13 = VM | last14 = Bauer | first14 = R | date = Apr 2013 | title = Polyacetylenes from Notopterygium incisum–new selective partial agonists of peroxisome proliferator-activated receptor-gamma | journal = PLOS ONE | volume = 8 | issue = 4| page = e61755 | doi = 10.1371/journal.pone.0061755 | pmid = 23630612 | pmc=3632601| bibcode = 2013PLoSO...861755A | doi-access = free }}{{cite journal | last1 = Ohnuma | first1 = T | last2 = Anan | first2 = E | last3 = Hoashi | first3 = R | last4 = Takeda | first4 = Y | last5 = Nishiyama | first5 = T | last6 = Ogura | first6 = K | last7 = Hiratsuka | first7 = A | year = 2011 | title = Dietary diacetylene falcarindiol induces phase 2 drug-metabolizing enzymes andblocks carbon tetrachloride-induced hepatotoxicity in mice through suppression of lipid peroxidation | journal = Biol Pharm Bull | volume = 34 | issue = 3| pages = 371–8 | pmid = 21372387 | doi=10.1248/bpb.34.371| doi-access = free }} and are studied as potential health-promoting nutraceuticals.{{cite journal | last1 = Christensen | first1 = LP | date = Jan 2011 | title = Aliphatic C₁₇-polyacetylenes of the falcarinol type as potential health promoting compounds in food plants of the Apiaceae family | journal = Recent Pat Food Nutr Agric | volume = 3 | issue = 1| pages = 64–77 | doi = 10.2174/2212798411103010064 | pmid = 21114468 }} Falcarindiol is the main compound responsible for bitterness in carrots, and is the most active among several polyynes with potential anticancer activity found in Devil's club (Oplopanax horridus). Other polyynes from plants include oenanthotoxin and cicutoxin, which are poisons found in water dropwort (Oenanthe spp.) and water hemlock (Cicuta spp.).

File:Ichthyothereol skeletal.png]]

Ichthyothere is a genus of plants whose active constituent is a polyyne called ichthyothereol. This compound is highly toxic to fish and mammals.{{cite journal|last1=Cascon|first1=Seiva C.|last2=Mors|first2=Walter B.|last3=Tursch|first3=Bernard M.|last4=Aplin|first4=Robin T.|last5=Durham|first5=Lois J.|title=Ichthyothereol and Its Acetate, the Active Polyacetylene Constituents of Ichthyothere terminalis (Spreng.) Malme, a Fish Poison from the Lower Amazon|journal=Journal of the American Chemical Society|volume=87|issue=22|year=1965|pages=5237–5241|issn=0002-7863|doi=10.1021/ja00950a044|pmid=5844817}} Ichthyothere terminalis leaves have traditionally been used to make poisoned bait by indigenous peoples of the lower Amazon basin.

File:Z-dihydromatricaria acid.png

Dihydromatricaria acid is a polyyne produced and secreted by soldier beetles as a chemical defense.{{cite book |title= Secret Weapons: Defenses of Insects, Spiders, Scorpions, and Other Many-legged Creatures |publisher= Harvard University Press |year= 2005 |first1= Thomas |last1= Eisner |first2= Maria |last2= Eisner |first3= Melody |last3= Siegler |isbn= 9780674018822 |chapter= 40. Chauliognathus lecontei (a soldier beetle) |pages= [https://archive.org/details/secretweaponsdef00eisn/page/185 185–188] |chapter-url-access= registration |chapter-url= https://archive.org/details/secretweaponsdef00eisn/page/185 }}

The octatetraynyl radicals and hexatriynyl radicals together with their ions are detected in space where hydrogen is rare.{{cite journal|last1=Duley|first1=W. W.|last2=Hu|first2=A.|title=Polyynes and interstellar carbon nanoparticles|journal=Astrophys. J.|date=2009|volume=698|issue=1|pages=808–811|doi=10.1088/0004-637X/698/1/808|bibcode=2009ApJ...698..808D|s2cid=119811921 |doi-access=free}} Moreover, there have been claims{{cite journal|last1=El Goresy|first1=A.|last2=Donnay|first2=G.|title=A New Allotropic Form of Carbon from the Ries Crater|journal=Science|date=1968|volume=151|issue=3839|pages=363–364|doi=10.1126/science.161.3839.363|pmid=17776738|bibcode=1968Sci...161..363E|s2cid=43744113}} that polyynes have been found in astronomical impact sites on Earth as part of the mineral chaoite, but this interpretation has been contested.{{cite journal|last1=Smith|first1=P. P. K.|last2=Busek|first2=P. R.|title=Carbyne Forms of Carbon: Do They Exist?|journal=Science|date=1982|volume=216|pages=984–986|doi=10.1126/science.216.4549.984|issue=4549|pmid=17809068|bibcode=1982Sci...216..984S|s2cid=13290442}} See Astrochemistry.

• Cyanopolyyne
• Isanolic acid
• Enediyne
• Enyne

{{Reflist}}

{{Molecules detected in outer space}}

Category:Conjugated hydrocarbons

Category:Astrochemistry