Carbomer 1503970 190630476 2008-02-11T15:07:03Z DragonflySixtyseven 62058 touchup In [[organic chemistry]], a '''carbomer''' is an expanded [[molecule]] obtained by insertion of a C<sub>2</sub> unit in a given molecule <ref>''Carbomers. I. A general concept of expanded molecules'' Remi Chauvin [[Tetrahedron Letters]] Volume 36, Issue 3 , 16 January '''1995''', Pages 397-400 {{doi|10.1016/0040-4039(94)02275-G}} </ref>. Carbomers differ from their templates in size but not in symmetry when each C–C single bond is replaced by at least one [[alkyne]] bond, and when a double bond is replaced by an [[allene]] bond. The size of the carbomer will continue to increase when more alkyne bonds are introduced and for this reason carbomers are also called '''carbo<sup>n</sup>-molecules''', where "n" is the number of acetylene or allene groups in an n-expansion unit. This concept, devised by Remi Chauvin in 1995, is aimed at introducing new chemical properties for existing chemical motifs. :[[Image:Carbo-benzene.png|500px|carbo-benzene]] Two representations exist for '''carbo-benzene''' (written as an [[Cyclooctadecanonaene|[18]annulene]] derivative: 1,2,4,5,7,8,I0,11,13,14,16,17-dodecadehydro[18]annulene), one has the aromatic core of [[benzene]] expanded, and one has the hydrogen [[substituent]]s expanded. The substituted benzene derivative hexaethynylbenzene is a known compound,<ref>''Hexaethynylbenzene'' Rainer Diercks, James C. Armstrong, Roland Boese, K. Peter C. Vollhardt. Hexaethynylbenzene. ''Angewandte Chemie International''. '''1986'''; 25(3):268-269. {{DOI|10.1002/anie.198602681}}</ref> and the core-expanded molecule also exists, although with the hydrogen atoms replaced by [[phenyl]] groups <ref>''Synthesis of the first 3,6,9,15,18,18-hexa-substituted-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro[18]annulenes with D6h-symmetry'' Yoshiyuki Kuwatani, Naoto Watanabe and Ikuo Ueda [[Tetrahedron Letters]] Volume 36, Issue 1 , 2 January '''1995''', Pages 119-122 {{doi|10.1016/0040-4039(94)02181-A}} </ref>. The final step in its [[organic synthesis]] is [[organic oxidation]] of the triol with [[stannous chloride]] and [[hydrochloric acid]] in [[diethyl ether]]. :[[Image:CarbobenzeneSynthesis.png|400px|carbo-benzene synthesis]] The [[proton NMR]] spectrum for this compound shows that the phenyl protons are shifted downfield compared to a proton position in benzene itself ([[chemical shift]] position for the [[aromatic ortho position|ortho]] proton is 9.49 ppm), suggesting the presence of a [[diamagnetic ring current]] and thus [[aromaticity]]. The total carbomer of benzene with core and periphery expanded (C<sub>30</sub>H<sub>6</sub>) only exists [[in silico]] <ref>''Total carbo-Mer of Benzene, Its carbo-Trannulene Form, and the Zigzag Nanotube Thereof'' Christine Lepetit, Chunhai Zou, and Remi Chauvin [[J. Org. Chem.]]; '''2006'''; 71(17) pp 6317 - 6324; (Article) {{DOI|10.1021/jo052551j}}</ref>. :[[Image:All-carbo-benzene.png|300px|Total carbomer of benzene]] Calculations predict a planar D<sub>6h</sub> structure with [[bond length]]s similar to the other two carbobenzenes. Its non-planar [[isomer]] is called "hexaethynyl-carbo-[6]trannulene" - a pun on the all-''cis'' [[annulene]]s - and resembles a [[cyclohexane]] ring. This hypothetical molecule is predicted to be more energetic by 65 [[calorie|kcal]]/[[mole (unit)|mol]]. ==Other carbomer meanings== Carbomer is also a [[tradename]] for a synthetic [[polymer]] of [[acrylic acid]]. Carbomers are used as [[emulsion]] [[Stabilizer (chemistry)|stabilizer]]s or [[thickening agent]]s in [[cosmetics|cosmetic products]]. They may be [[homopolymer]]s of acrylic acid, [[crosslinked]] with an [[allyl]] [[ether]] [[pentaerythritol]], allyl ether of [[sucrose]], or allyl ether of [[propylene]]. ==References== <div class="references-small"> <references/> </div> [[Category:Cosmetic chemicals]] [[Category:Polyacrylates]] [[Category:alkynes]] [[ru:Карбополы]]