Polar Effects Control the Gas-Phase Reactivity of para-Benzyne Analogs

Huaming Sheng, Xin Ma, Hao Ran Lei, Jacob Milton, Weijuan Tang, Chunfen Jin, Jinshan Gao, Ashley M. Wittrig, Enada F. Archibold, John J. Nash, Hilkka I. Kenttämaa

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Abstract

We report herein a gas-phase reactivity study on a para-benzyne cation and its three cyano-substituted, isomeric derivatives performed using a dual-linear quadrupole ion trap mass spectrometer. All four biradicals were found to undergo primary and secondary radical reactions analogous to those observed for the related monoradicals, indicating the presence of two reactive radical sites. The reactivity of all biradicals is substantially lower than that of the related monoradicals, as expected based on the singlet ground states of the biradicals. The cyano-substituted biradicals show substantially greater reactivity than the analogous unsubstituted biradical. The greater reactivity is rationalized by the substantially greater (calculated) electron affinity of the radical sites of the cyano-substituted biradicals, which results in stabilization of their transition states through polar effects. This finding is in contrast to the long-standing thinking that the magnitude of the singlet-triplet splitting controls the reactivity of para-benzynes.

Original languageEnglish
Pages (from-to)2839-2842
Number of pages4
JournalChemPhysChem
Volume19
Issue number21
DOIs
StatePublished - 5 Nov 2018

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Keywords

  • Biradical
  • electron affinities
  • gas-phase reactions
  • mass spectrometry
  • para-benzyne

Cite this

Sheng, H., Ma, X., Lei, H. R., Milton, J., Tang, W., Jin, C., Gao, J., Wittrig, A. M., Archibold, E. F., Nash, J. J., & Kenttämaa, H. I. (2018). Polar Effects Control the Gas-Phase Reactivity of para-Benzyne Analogs. ChemPhysChem, 19(21), 2839-2842. https://doi.org/10.1002/cphc.201800646