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Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on Covalent-Ionic Resonance Energy Andrew M. James, Croix J Laconsay, and John Morrison Galbraith J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b02988 • Publication Date (Web): 21 Jun 2017 Downloaded from http://pubs.acs.org on June 22, 2017
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The Journal of Physical Chemistry
Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on CovalentIonic Resonance Energy Andrew M. James,† Croix J. Laconsay,‡ and John Morrison Galbraith Department of Chemistry, Biochemistry, and Physics, Marist College, 3399 North Road, Poughkeepsie, NY 12601, USA
[email protected] RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) †
Current Address: Department of Chemistry, Virginia Tech, Blacksburg, VA 24061, USA.
[email protected] ‡
Current Address: Department of Chemistry, University of California Davis, One Shields Ave., Davis,
CA 95616.
[email protected] ABSTRACT: Bond dissociation energies and resonance energies for HnA-BHm molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory.
Following Pauling’s original scheme, and using the
rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, ACS Paragon Plus Environment
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The Journal of Physical Chemistry
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and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na respectively. The chargeshift corrected electronegativity values presented herein follow the same general trends as Pauling’s original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, H3C-F, Li-CH3, and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as “polar charge-shift” rather than simply “charge-shift”. Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH3, -NH2, -OH, and –F have on the resonance energy (
