Styrene energetics and characterization of its conjugate base: An example of isotopic labeling gone awry

Fattahi, A ; Sharif University of Technology | 2017

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  1. Type of Document: Article
  2. DOI: 10.1016/j.ijms.2016.03.009
  3. Publisher: Elsevier B.V , 2017
  4. Abstract:
  5. The equilibrium acidity of styrene was measured (ΔH°acid(PhCH[dbnd]CH2) = 390.6 ± 0.5 kcal mol−1) and its deprotonation site was revised from the ortho position on the aromatic ring to the α-hydrogen atom based upon deuterium-labeling studies and extensive computations. Somewhat surprisingly, the nature of the anionic base plays a critical role in properly determining the ionization site and avoiding misleading results due to extraordinary hydrogen–deuterium exchange. Bracketing the electron affinity of α-styryl radical (PhC[rad][dbnd]CH2, 23.1 ± 3.4 kcal mol−1) enabled the α-C[sbnd]H bond dissociation energy (100.1 ± 3.4 kcal mol−1) of styrene and the effect of a phenyl substituent at an sp2-hybridized carbon to be determined. These results were compared to B3LYP, M06-2X, G3 and G4 computations. © 2016 Elsevier B.V
  6. Keywords:
  7. Bond dissociation energy ; Gas-phase energetics ; Hydrogen–deuterium exchange ; Styrene ; α-Styryl radical
  8. Source: International Journal of Mass Spectrometry ; Volume 413 , 2017 , Pages 163-167 ; 13873806 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/pii/S138738061630015X