Resorcinarene 3998467 220319604 2008-06-19T08:09:26Z 213.151.66.234 A '''resorcinarene''' (also '''resorcarene''' or '''calix[4]resorcinarene''') is a [[macrocycle]], or a [[Cyclic compound|cyclic]] [[oligomer]], based on the condensation of [[resorcinol]] (1,3-dihydroxybenzene) and an [[aldehyde]]. Resorcinarenes are a type of [[calixarene]]. ==Synthesis== The resorcinarene macrocycle is typically prepared by condensation of [[resorcinol]] and an [[aldehyde]] in concentrated [[acid]] solution.<sup>[1]</sup><sup>[2]</sup> Recrystallization typically gives the desired isomer in quite pure form. However, for certain aldehydes, the reaction conditions lead to significant [[by-product]]s. Therefore, alternative condensation conditions have been developed, including the use of [[Lewis acid]] catalysts. [[image:Resorcinarene_synth.gif|center|Preparation of resorcin[4]arenes from resorcinol and an aldehyde.]] A [[green chemistry]] procedure was recently developed using solvent-free conditions: resorcinol, an aldehyde, and [[P-Toluenesulfonic acid|''p''-toluenesulfonic acid]] are ground together in a [[mortar and pestle]] at low temperature.<sup>[3]</sup> A paste-like solid forms upon sitting for several minutes, which can be washed with water and crystallized to give the desired resorcinarene. Under each of these conditions, [[aromatic]] aldehydes react much faster, but less stereoselectively than [[aliphatic]] aldehydes, and the reaction frequently leads to a mixture of desired and undesired products. ==Structure== Resorcinarenes can be characterized by a wide '''upper rim''' and a narrow '''lower rim'''. The upper rim includes eight [[hydroxyl]] groups that can participate in [[hydrogen bonding]] interactions. Depending on the aldehyde starting material, the lower rim includes four appending groups, usually chosen to give optimal soubility. The resorcin[n]arene [[IUPAC nomenclature|nomenclature]] is analogous to that of calix[n]arenes, in which 'n' represents the number of repeating units in the ring. [[Pyrogallolarenes]] are related macrocycles derived from the condensation of [[pyrogallol]] (1,2,3-trihydroxybenzene) with an aldehyde. ==History== During the late 19th century, [[Adolf von Baeyer]] noted that the condensation reaction of [[resorcinol]] and [[benzaldehyde]] gave a mixture of products that was beyond the characterization methods of that time. Over the following century, the product mixture was more fully characterized by [[X-ray crystallography]] and [[Nuclear Magnetic Resonance]] and found to include general structure shown above and several other [[stereoisomers]]. ==Supramolecular Chemistry== Yasuhiro Aoyama's research group at [[Kyoto University]] first noted the potential for resorcinarenes to interact with other molecules as a [[host-guest complex]].<sup>[4]</sup> It was later found that resorcinarenes and pyrogallolarenes [[molecular self-assembly|self-assemble]] into to larger supramolecular structures. Both in the crystalline state and in [[organic solvent]]s, six resorcinarene molecules are known to form hexamers with an internal volume of around one cubic [[nanometer]] (nanocapsules) and shapes similar to the [[Archimedean solid]]s.<sup>[5]</sup> [[Hydrogen bonds]] appear to hold the assembly together. A number of solvent or other molecules reside inside.<sup>[6]</sup> The resorcinarene is also the basic structural unit for other molecular recognition scaffolds. A number of chemists, including [[Nobel prize|Nobel-laureate]] [[Donald J. Cram]], constructed novel molecular structures based on this macrocycle, namely [[cavitand]]s and [[carcerand]]s. ==External links== *[http://www.chem.missouri.edu/faculty/Atwood/research.html Jerry Atwood Research Group] *[http://www.scripps.edu/skaggs/rebek/ Julius Rebek, Jr. Research Group] ==References== * <sup>[1]</sup> {{cite journal | author=Högberg AGS | title=| journal=Journal of Organic Chemistry | volume=45. | issue= | year=1980 | pages=4498–4500 | doi=10.1021/jo01310a046}} * <sup>[2]</sup> {{cite journal | author=Högberg AGS | title=| journal=[[Journal of the American Chemical Society]] | volume=102. | issue= | year=1980 | pages=6046–6050 | doi=10.1021/ja00539a012}} * <sup>[3]</sup> {{cite journal | author=Antesberger J, Cave GW, Ferrarelli MC, Heaven MW, Raston CL, Atwood JL | title=Solvent-free, direct synthesis of supramolecular nano-capsules | journal=Chemical Communications (Cambridge, England) | volume=. | issue=7 | year=2005 | pages=892–894 | pmid=15700072 | doi=10.1039/b412251h}} * <sup>[4]</sup> {{cite journal | author=Aoyama Y, Tanaka Y, Toi H, Ogoshi H | title= | journal=[[Journal of the American Chemical Society]] | volume=110 | issue= | year=1988 | pages=634–635 | doi= 10.1021/ja00210a073}} * <sup>[5]</sup> {{cite journal | author=Atwood JL, Barbour LJ, Jerga A | title=Organization of the interior of molecular capsules by hydrogen bonding | journal=[[Proceedings of the National Academy of Sciences]] | volume=99 | issue=8 | year=2002 | pages=4837–4841 | pmid=11943875 | doi=10.1073/pnas.082659799}} * <sup>[6]</sup> {{cite journal | author=Shivanyuk A, Rebek J | title=Reversible encapsulation by self-assembling resorcinarene subunits | journal=[[Proceedings of the National Academy of Sciences]] | volume=98 | issue= | year=2001 | pages=7662–7665 | doi=10.1073/pnas.141226898}} * <sup>[7]</sup> {{cite journal | author=Palmer LC, Shivanyuk A, Yamanaka M, Rebek J | title=Resorcinarene assemblies as synthetic receptors | journal=Chemical Communications (Cambridge, England) | volume= | issue=7 | year=2005 | pages=857–858 | doi=10.1039/b414252g}} [[Category:supramolecular chemistry]] [[Category:Macrocycles]]