Publication Date:
2010-08-28
Description:
Transition state structures are central to the rates and outcomes of chemical reactions, but their fleeting existence often leaves their properties to be inferred rather than observed. By treating polybutadiene with a difluorocarbene source, we embedded gem-difluorocyclopropanes (gDFCs) along the polymer backbone. We report that mechanochemical activation of the polymer under tension opens the gDFCs and traps a 1,3-diradical that is formally a transition state in their stress-free electrocyclic isomerization. The trapped diradical lives long enough that we can observe its noncanonical participation in bimolecular addition reactions. Furthermore, the application of a transient tensile force induces a net isomerization of the trans-gDFC into its less-stable cis isomer, leading to the counterintuitive result that the gDFC contracts in response to a transient force of extension.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lenhardt, Jeremy M -- Ong, Mitchell T -- Choe, Robert -- Evenhuis, Christian R -- Martinez, Todd J -- Craig, Stephen L -- New York, N.Y. -- Science. 2010 Aug 27;329(5995):1057-60. doi: 10.1126/science.1193412.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Duke University, Durham, NC 27708, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20798315" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
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Chemistry and Pharmacology
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Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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