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In organic chemistry, a ''carbo''-mer (often carbo-mer or carbomer) is an expanded molecule obtained by 
One (above right) expands each C-H bond to C-C≡C-H, making hexaethynylbenzene, a substituted benzene derivative.
One (above left) expands each C=C and C≡C bond of the benzene core, making 1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro 8nnulene. An analog of this molecule, with the hydrogen atoms replaced by phenyl groups, 3,6,9,12,15,18-hexaphenyl-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro 8nnulene, is stable. Its proton NMR spectrum shows that the phenyl protons are shifted downfield compared to a proton position in benzene itself ( chemical shift position for the ortho proton is 9.49 ppm), suggesting the presence of a diamagnetic ring current and thus aromaticity. The final step in its 
With both core and periphery expanded, the total ''carbo''-mer of benzene (C30H6) only exists ''
Calculations predict a planar D6h structure with bond lengths similar to the other two carbobenzenes. Its non-planar
insertion
Insertion may refer to:
*Insertion (anatomy), the point of a tendon or ligament onto the skeleton or other part of the body
*Insertion (genetics), the addition of DNA into a genetic sequence
*Insertion, several meanings in medicine, see ICD-10-PCS
...
of C2 units into a given molecule. ''Carbo''-mers differ from their templates in size but not in symmetry when each C–C single bond is replaced by an alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
bond C-C≡C-C, each C=C double bond is replaced by an allene bond C=C=C=C, and each C≡C triple bond is replaced by C≡C-C≡C. The size of the ''carbo''-mer continues to increase when more C2 units are inserted, so ''carbo''-mers are also called ''carbo''n-molecules, where "n" is the number of acetylene or allene groups in an n-expansion unit. This concept, devised by Rémi Chauvin in 1995, is aimed at introducing new chemical properties for existing chemical motifs.
Two distinct expansions of benzene can be called ''carbo''-benzene (C18H6):
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One (above right) expands each C-H bond to C-C≡C-H, making hexaethynylbenzene, a substituted benzene derivative.
One (above left) expands each C=C and C≡C bond of the benzene core, making 1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro 8nnulene. An analog of this molecule, with the hydrogen atoms replaced by phenyl groups, 3,6,9,12,15,18-hexaphenyl-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro 8nnulene, is stable. Its proton NMR spectrum shows that the phenyl protons are shifted downfield compared to a proton position in benzene itself ( chemical shift position for the ortho proton is 9.49 ppm), suggesting the presence of a diamagnetic ring current and thus aromaticity. The final step in its organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
is reaction of the triol with stannous chloride and hydrochloric acid in diethyl ether:
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With both core and periphery expanded, the total ''carbo''-mer of benzene (C30H6) only exists ''in silico
In biology and other experimental sciences, an ''in silico'' experiment is one performed on computer or via computer simulation. The phrase is pseudo-Latin for 'in silicon' (correct la, in silicio), referring to silicon in computer chips. It ...
'' (computer simulation).''Total carbo-Mer of Benzene, Its carbo-Trannulene Form, and the Zigzag Nanotube Thereof'' Christine Lepetit, Chunhai Zou, and Remi Chauvin J. Org. Chem.
''The Journal of Organic Chemistry'', colloquially known as ''JOC'', is a peer-reviewed scientific journal for original contributions of fundamental research in all branches of theory and practice in organic and bioorganic chemistry. It is publ ...
; 2006; 71(17) pp 6317 - 6324; (Article)
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Calculations predict a planar D6h structure with bond lengths similar to the other two carbobenzenes. Its non-planar isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
is called "hexaethynyl-carbo- rannulene" - a pun on the all-''cis'' annulenes - and resembles a cyclohexane
Cyclohexane is a cycloalkane with the molecular formula . Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cyclohexan ...
ring. This hypothetical molecule is predicted to be more energetic by 65 kcal/ mol.
References
{{Reflist Alkyne derivatives