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Mechanochemical Ring-Opening of Allylic Epoxides

Publication ,  Journal Article
Barbee, MH; Wang, J; Kouznetsova, T; Lu, M; Craig, SL
Published in: Macromolecules
August 27, 2019

Recent successes in covalent polymer mechanochemistry might more easily be translated to stress-responsive bulk materials if easily scalable and minimalist mechanophores were identified. Epoxides represent attractive modifications of unsaturated polymer backbones for this purpose, but they suffer from limited mechanical reactivity. Here, we report that placing alkenes adjacent to cis-epoxide mechanophores along a polymer backbone results in ring-opening to carbonyl ylides during sonication, whereas epoxides with an adjacent saturated, linear alkyl chain do not. Upon release, tension-trapped ylides preferentially close to their trans-epoxides in accordance with the Woodward-Hoffmann rules. The reactivity of carbonyl ylides is exploited to tag the activated species with spectroscopic labels and to facilitate force-induced cross-linking through a reaction with pendant alcohols on co-polymers. The alkene effect is attributed to a combination of lower activation energy of the reaction (δG‡) and greater force-coupled change in the length as the reaction proceeds from the ground to transition state (δx‡) relative to epoxides without the alkene. Even with alkene assistance, mechanochemical reactivity remains low; single-molecule force spectroscopy establishes that at ∼2500 pN ring-opening proceeds with a rate constant that is less than approximately 5 s-1 in toluene.

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Published In

Macromolecules

DOI

EISSN

1520-5835

ISSN

0024-9297

Publication Date

August 27, 2019

Volume

52

Issue

16

Start / End Page

6234 / 6240

Related Subject Headings

  • Polymers
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences
 

Citation

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Barbee, M. H., Wang, J., Kouznetsova, T., Lu, M., & Craig, S. L. (2019). Mechanochemical Ring-Opening of Allylic Epoxides. Macromolecules, 52(16), 6234–6240. https://doi.org/10.1021/acs.macromol.9b01190
Barbee, M. H., J. Wang, T. Kouznetsova, M. Lu, and S. L. Craig. “Mechanochemical Ring-Opening of Allylic Epoxides.” Macromolecules 52, no. 16 (August 27, 2019): 6234–40. https://doi.org/10.1021/acs.macromol.9b01190.
Barbee MH, Wang J, Kouznetsova T, Lu M, Craig SL. Mechanochemical Ring-Opening of Allylic Epoxides. Macromolecules. 2019 Aug 27;52(16):6234–40.
Barbee, M. H., et al. “Mechanochemical Ring-Opening of Allylic Epoxides.” Macromolecules, vol. 52, no. 16, Aug. 2019, pp. 6234–40. Scopus, doi:10.1021/acs.macromol.9b01190.
Barbee MH, Wang J, Kouznetsova T, Lu M, Craig SL. Mechanochemical Ring-Opening of Allylic Epoxides. Macromolecules. 2019 Aug 27;52(16):6234–6240.
Journal cover image

Published In

Macromolecules

DOI

EISSN

1520-5835

ISSN

0024-9297

Publication Date

August 27, 2019

Volume

52

Issue

16

Start / End Page

6234 / 6240

Related Subject Headings

  • Polymers
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences