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Hudson CE, McAdoo DJ. Circumvention of orbital symmetry restraints by 1,3-H-shifts of enolic radical cations. J Am Soc Mass Spectrom. 2004;15(7):972-81doi: 10.1016/j.jasms.2004.03.011.
Hudson, C. E., & McAdoo, D. J. (2004). Circumvention of orbital symmetry restraints by 1,3-H-shifts of enolic radical cations. Journal of the American Society for Mass Spectrometry, 15(7), 972-81. https://doi.org/10.1016/j.jasms.2004.03.011
Hudson, Charles E, and McAdoo, David J. "Circumvention of orbital symmetry restraints by 1,3-H-shifts of enolic radical cations." Journal of the American Society for Mass Spectrometry vol. 15,7 (2004): 972-81. doi: https://doi.org/10.1016/j.jasms.2004.03.011
Hudson CE, McAdoo DJ. Circumvention of orbital symmetry restraints by 1,3-H-shifts of enolic radical cations. J Am Soc Mass Spectrom. 2004 Jul;15(7):972-81. doi: 10.1016/j.jasms.2004.03.011. PMID: 15234356.
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J Am Soc Mass Spectrom. 2004 Jul;15(7):972-81. doi: 10.1016/j.jasms.2004.03.011.

Circumvention of orbital symmetry restraints by 1,3-H-shifts of enolic radical cations.

Journal of the American Society for Mass Spectrometry

Charles E Hudson, David J McAdoo

Affiliations

  1. Department of Neurosciences and Cell Biology, University of Texas Medical Branch, Galveston, 77555, USA.

PMID: 15234356 DOI: 10.1016/j.jasms.2004.03.011

Abstract

The reaction coordinates of 1,3-H-shifts across double bonds are traced by theory for three reactions, CH(3)C(OH)CH(2)(+*) (1) --> CH(3)C(O(+*))CH(3) (2), CH(2)C(OH)(2)(+*) (3) --> CH(3)CO(2)H(+*) (4) and CH(3)C(OH)CH(2)(+*) (1) --> CH(2)C(OH)CH(3)(+*) (1'), to explore how the need to conserve orbital symmetry influences the pathways for these reactions. In the first and second reactions, prior to the start of the H-transfer the methylene rotates from being in the skeletal plane to being bisected by it. Thus these reactions are neither antarafacial nor suprafacial, but precisely between those possibilities. This stems from a counterbalancing between the need to conserve orbital symmetry and the large distorting forces required to attain an allowed antarafacial transition state. In contrast to the first two reactions, 1 --> 1' follows a suprafacial pathway. However, this pathway does not violate conservation of orbital symmetry, as it utilizes lower lying orbitals of appropriate symmetry rather than the antisymmetric uppermost occupied allyl-type orbital. Changes in geometry which presumably produce asymmetric vibrational excitation and the unequal losses of methyl that follow 1 --> 2, i.e., nonergodic behavior, are also characterized.

References

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  2. J Am Chem Soc. 2002 Jul 24;124(29):8512-3 - PubMed
  3. J Org Chem. 2003 Apr 4;68(7):2735-40 - PubMed

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