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A heterocumulene is a molecule or ion containing a chain of at least three double bonds between consecutive atoms, in which one or more atoms in the doubly bonded chain is a heteroatom. Such species are analogous to a cumulene in which the chain of doubly bonded atoms contains only carbon, except that at least one carbon is replaced by a heteroatom.[1] Some authors relax the definition to include species with chains of only two double bonds between consecutive atoms,[2] also known as heteroallenes. Because of the double bond rule, heterocumulenes are rarely isolated. Instead they tend to polymerize. Many are however common in the interstellar medium, where they exist as a dilute gas. Most of the longer ones are very unstable and reactive, and thus have a transient existence, or can only survive when dilute or in an inert matrix. Molecular clouds in space are very dilute and allow heterocumulenes to exist long enough to be detected. Some simple heterocumulenes are common chemicals or ions. These include carbon dioxide, carbon disulfide, carbon diselenide, cyanate, thiocyanate. Some definitions of heterocumulenes include compounds that contain concatenated double bonds with more than one element, but may have other parts to them. This class includes ketene, sulfur diimide, sulfine and dicyclohexylcarbodiimide. Some heterocumulenes can act as ligands with various metals.


Some energised herterocumulenes can cyclise by bending into a circle and bonding the two ends of the chain. Molecules that can do this are CCCB, CCCAl, CCCSi, CCCN, or CCCP.[3]

Other four atom heterocumulenes include CCBO, tricarbon monoxide (CCCO) and CCCS Four atom heterocumulenes when cyclised can have two forms. In the kite (or rhombic) form, a triangle of carbon has two of its atoms bonded to the heteroatom. In the fan form the hetero atom links to three carbon atoms arranged in a fan shape. CCCSi has linear, rhombic or fan isomers. The rhombic form is known in space near the carbon star IRC+10216.

CCCCO cyclises to a three-member ring.[3] CCCCN undergoes an isonitrile conversion.[3]


Other known five atom heterocumulenes include CCBCC, CCCCB, CCOCC, CCCCSi, CNCCO, HCCCO, HCCCS, and NCCCN. CCCCSi is known as a linear molecule in space.

CCCCBO turns into a six-member ring. Other six atom heterocumulenes include OCCCCN and HCNCNH.

Seven atom heterocumulenes include NCCCCCN, HCCBCCH.

A known nine atom heterocumulene is HCCCCCCCH.

Thiocumulenes have a sulfur atom. They include dicarbon monosulfide CCS and tricarbon monosulfide CCCS both known from molecular clouds.[4] SCnS chains can be made by laser ablation with n up to 27.[5]

Table of molecules

This table lists heterocumulene molecules. Heterocumulenes are supposed to be straight, but some combinations of elements result in bent or cyclic molecules.

one kind of heteroatom
heteroatom 1 carbon 2 carbon 3 carbon 4 carbon 5 carbon 6 carbon 7 carbon 8 carbon 9 carbon
O OCO CCO[7] CCCO OCCCO C4O[7] C4O2 OC5O C6O[7] C8O[7]
Si CCSi bent CCCSi ring CCCCSi[6] C6Si[6]
S SCS CCS CCCS SCCCS C4S[8] SCCCCS[8] C5S[8] SC5S[8][9] C6S[10] SC7S[10] SC9S[10]
Cl CCCl CCCCl is bent
Se CSe2 SeCCCSe[11]

Two different hetero atoms

atom 1 H B N O F Al Si P S Cl As Se Br
S HC2-8S (HCS bent)[12] NCS (NCCS bent) NC3-7S[12] OCS
Se -SeCN


  1. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "heterocumulenes". doi:10.1351/goldbook.H02797
  2. Kumar, Akshai; Samuelson, Ashoka G. (January 2011). "Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study". Journal of Chemical Sciences 123 (1): 29–36. doi:10.1007/s12039-011-0069-4. 
  3. 3.0 3.1 3.2 Wang, Tianfang; Bowie, John H. (November 2011). "Studies of cyclization reactions of linear cumulenes and heterocumulenes using the neutralization-reionization procedure and/or ab initio calculations". Mass Spectrometry Reviews 30 (6): 1225–1241. doi:10.1002/mas.20328. PMID 21400561. Bibcode2011MSRv...30.1225W. 
  4. Yamamoto, Satoshi; Saito, Shuji; Kawaguchi, Kentarou; Kaifu, Norio; Suzuki, Hiroko (June 1987). "Laboratory detection of a new carbon-chain molecule C3S and its astronomical identification". The Astrophysical Journal 317: L119. doi:10.1086/184924. Bibcode1987ApJ...317L.119Y. 
  5. Burnin, Andrei; BelBruno, Joseph J. (November 2003). "SCnS Linear Chain Production by Direct Laser Ablation". The Journal of Physical Chemistry A 107 (45): 9547–9553. doi:10.1021/jp0304071. Bibcode2003JPCA..107.9547B. 
  6. 6.0 6.1 6.2 6.3 6.4 6.5 Botschwina, Peter (2003). "Spectroscopic properties of interstellar molecules: Theory and experiment". Physical Chemistry Chemical Physics 5 (16): 3337. doi:10.1039/b303753n. Bibcode2003PCCP....5.3337B. 
  7. 7.0 7.1 7.2 7.3 Ohshima, Yasuhiro; Endo, Yasuki; Ogata, Teruhiko (22 January 1995). "Fourier‐transform microwave spectroscopy of triplet carbon monoxides, C2O, C4O, C6O, and C8O". The Journal of Chemical Physics 102 (4): 1493–1500. doi:10.1063/1.468881. Bibcode1995JChPh.102.1493O. 
  8. 8.0 8.1 8.2 8.3 Szczepanski, Jan; Hodyss, Robert; Fuller, Jason; Vala, Martin (April 1999). "Infrared Absorption Spectroscopy of Small Carbon−Sulfur Clusters Isolated in Solid Ar". The Journal of Physical Chemistry A 103 (16): 2975–2981. doi:10.1021/jp984700q. Bibcode1999JPCA..103.2975S. 
  9. Thorwirth, S.; Salomon, T.; Fanghänel, S.; Kozubal, J.R.; Dudek, J.B. (September 2017). "High-resolution infrared fingerprints of carbon-sulfur clusters: The ν1 band of C5S". Chemical Physics Letters 684: 262–266. doi:10.1016/j.cplett.2017.06.032. Bibcode2017CPL...684..262T. 
  10. 10.0 10.1 10.2 Wang, Haiyan; Szczepanski, Jan; Cooke, Andrew; Brucat, Philip; Vala, Martin (2005). "Vibrational absorption spectra of CnS (n = 2, 6) and CnS2 (n = 7, 9, 11, 13, 15) linear carbon-sulfur clusters". International Journal of Quantum Chemistry 102 (5): 806–819. doi:10.1002/qua.20383. Bibcode2005IJQC..102..806W. 
  11. Pu, Liang; Zhao, Xiao; Zhang, Zhong; King, R. Bruce (May 2017). "Heavier Carbon Subchalcogenides as C3 Sources for Tungsten-Capped Cumulenes: A Theoretical Study". Inorganic Chemistry 56 (10): 5567–5576. doi:10.1021/acs.inorgchem.6b02958. PMID 28459557. 
  12. 12.0 12.1 McCarthy, M. C.; Cooksy, A. L.; Mohamed, S.; Gordon, V. D.; Thaddeus, P. (February 2003). "Rotational Spectra of the Nitrogen‐Sulfur Carbon Chains NCnS, n = 1–7". The Astrophysical Journal Supplement Series 144 (2): 287–297. doi:10.1086/344727. Bibcode2003ApJS..144..287M.