Trapping a diradical transition state by mechanochemical polymer extension.

Journal Article

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.

Full Text

Duke Authors

Cited Authors

  • Lenhardt, JM; Ong, MT; Choe, R; Evenhuis, CR; Martinez, TJ; Craig, SL

Published Date

  • August 27, 2010

Published In

Volume / Issue

  • 329 / 5995

Start / End Page

  • 1057 - 1060

PubMed ID

  • 20798315

Electronic International Standard Serial Number (EISSN)

  • 1095-9203

Digital Object Identifier (DOI)

  • 10.1126/science.1193412

Language

  • eng

Conference Location

  • United States