https://www.wikidoc.org/index.php?title=Intramolecular&feed=atom&action=historyIntramolecular - Revision history2024-03-29T07:09:18ZRevision history for this page on the wikiMediaWiki 1.40.0https://www.wikidoc.org/index.php?title=Intramolecular&diff=717297&oldid=prevWikiBot: Robot: Automated text replacement (-{{WikiDoc Cardiology Network Infobox}} +, -<references /> +{{reflist|2}}, -{{reflist}} +{{reflist|2}})2012-09-04T18:40:17Z<p>Robot: Automated text replacement (-{{WikiDoc Cardiology Network Infobox}} +, -<references /> +{{reflist|2}}, -{{reflist}} +{{reflist|2}})</p>
<p><b>New page</b></p><div>'''Intramolecular''' in [[chemistry]] describes a process or characteristic limited within the structure of a single [[molecule]]; a property or phenomenon limited to the extent of a single molecule. <br />
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== Examples ==<br />
* intramolecular hydride transfer (transfer of a hydride ion from one part to another within the same molecule)<br />
* intramolecular hydrogen bond (a hydrogen bond formed between two functional groups of the same molecule)<br />
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In intramolecular [[organic reaction]]s, two reaction sites are contained within a single molecule. This creates a very high effective [[concentration]] (resulting in high [[reaction rate]]s) and therefore many intramolecular reactions take place that would not occur as an [[intermolecular]] reaction between two compounds. <br />
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Examples of intramolecular reactions are the [[Smiles rearrangement]], the [[Dieckmann condensation]] and the [[Madelung synthesis]].<br />
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==Molecular tethers==<br />
In a niche concept called '''molecular tethers''' otherwise intermolecular reactions can be made temporarily intramolecular by anchoring both reactions by a [[tether]] with all the advantages associated to it. Popular choices of tether contain a [[carbonate ester]], [[boronic ester]], [[silyl ether]] or a [[silyl acetal]] link ('''silicon tethers''') which are fairly inert in many organic reactions yet can be cleaved by specific reagents. Main hurdle for this strategy to work is selecting the proper length for the tether and making sure reactive groups have an optimal orientation with respect to each other. An examples is a [[Pauson-Khand reaction]] of a alkene and an alkyne tethered together via a silyl ether <ref>''The use of silicon-based tethers for the Pauson-Khand reaction'' Dobbs A, Miller I, Martinovic S<br />
[[Beilstein Journal of Organic Chemistry]], '''2007''' 3:21 ( 6 July 2007 ) [http://bjoc.beilstein-journals.org/content/pdf/1860-5397-3-21.pdf Article link]</ref> <br />
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[[Image:PausobnKhandSiliconTether.png|300px|Pauson-Khand silicon tether]]<br />
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In this particular reaction the tether angle bringing the reactive groups together is effectively reduced by placing [[isopropyl]] groups on the silicon atom via the [[Thorpe-Ingold effect]]. No reaction takes place when these bulky groups are replaced by smaller methyl groups.<br />
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Another example is a [[photochemical]] [2+2][[cycloaddition]] with two alkene groups tethered through a silicon acetal group (racemic, the other [[enantiomer]] not depicted) which is subsequently cleaved by [[TBAF]] yielding the endo-diol. <br />
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:[[Image:CycloadditionSiliconTether.png|400px|Cycloaddition silicon tether]]<br />
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Without the tether the [[exo isomer]] forms <ref>''Diastereoselective intramolecular photochemical [2 + 2] cycloaddition reactions of tethered l-(+)-valinol derived tetrahydrophthalimides'' Kevin I. Booker-Milburn, Sirin Gulten and Andrew Sharpe [[Chem. Commun.]], '''1997''', 1385 - 1386, {{DOI|10.1039/a702386c}}</ref>. <br />
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== See also ==<br />
* [[Intermolecular]]<br />
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==References==<br />
{{reflist|2}}<br />
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[[Category:Molecular physics]]<br />
[[Category:organic chemistry]]<br />
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