Substituent Effects in Mechanochemical Allowed and Forbidden Cyclobutene Ring-Opening Reactions.

Journal Article (Journal Article)

Woodward and Hoffman once jested that a very powerful Maxwell demon could seize a molecule of cyclobutene at its methylene groups and tear it open in a disrotatory fashion to obtain butadiene (Woodward, R. B.; Hoffmann, R. The Conservation of Orbital Symmetry. Angew. Chem., Int. Ed . 1969 , 8 , 781-853). Nearly 40 years later, that demon was discovered, and the field of covalent polymer mechanochemistry was born. In the decade since our demon was befriended, many fundamental investigations have been undertaken to build up our understanding of force-modified pathways for electrocyclic ring-opening reactions. Here, we seek to extend that fundamental understanding by exploring substituent effects in allowed and forbidden ring-opening reactions of cyclobutene (CBE) and benzocyclobutene (BCB) using a combination of single-molecule force spectroscopy (SMFS) and computation. We show that, while the forbidden ring-opening of cis -BCB occurs at a lower force than the allowed ring-opening of trans -BCB on the time scale of the SMFS experiment, the opposite is true for cis - and trans -CBE. Such a reactivity flip is explained through computational analysis and discussion of the so-called allowed/forbidden gap.

Full Text

Duke Authors

Cited Authors

  • Brown, CL; Bowser, BH; Meisner, J; Kouznetsova, TB; Seritan, S; Martinez, TJ; Craig, SL

Published Date

  • March 2021

Published In

Volume / Issue

  • 143 / 10

Start / End Page

  • 3846 - 3855

PubMed ID

  • 33667078

Electronic International Standard Serial Number (EISSN)

  • 1520-5126

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/jacs.0c12088

Language

  • eng