Journalartikel

Jahr der Veröffentlichung: 2010

Seiten: 7273-7275

Zeitschrift: Journal of the American Chemical Society

Bandnummer: 132

Heftnummer: 21

DOI Link: https://doi.org/10.1021/ja9107885

Verlag: American Chemical Society

Abstract: 

Phenylhydroxycarbene (Ph−C−OH, 1), the parent of all
arylhydroxycarbenes, was generated by high-vacuum flash pyrolysis of
phenylglyoxylic acid at 600 °C and spectroscopically characterized (IR,
UV−vis) via immediate matrix isolation in solid Ar at 11 K. The identity
of 1 was unequivocally confirmed by the precise agreement
between the observed IR bands and (unscaled) anharmonic vibrational
frequencies computed from a CCSD(T)/cc-pVDZ quartic force field. The
UV−vis spectrum of 1 displays a broad band with maximum
absorption at 500 ± 25 nm (2.5 ± 0.1 eV) that extends to ∼640 nm (1.9
eV), in full accord with combined CCSD(T)/cc-pVQZ and EOM-CCSD/cc-pVTZ
computations that yield a gas-phase vertical (adiabatic) excitation
energy of 2.7 (1.9) eV. Unlike singlet phenylchlorocarbene, 1 does not undergo photochemical ring expansion. Instead, 1 exhibits quantum-mechanical hydrogen tunneling to benzaldehyde underneath a formidable barrier of 28.8 kcal mol⁻¹,
even at cryogenic temperatures. The remarkable hydrogen tunneling
mechanism is supported by the temperature insensitivity of the observed
half-life (2.5 h) and substantiated by a comparable theoretical
half-life (3.3 h) determined from high-level barrier penetration
integrals computed along the intrinsic reaction path. As expected,
deuteration turns off the tunneling mechanism, so d-1 is stable under otherwise identical conditions.

Harvard-Zitierstil: Gerbig, D., Reisenauer, H., Wu, C., Ley, D., Allen, W. and Schreiner, P. (2010) Phenylhydroxycarbene, Journal of the American Chemical Society, 132(21), pp. 7273-7275. https://doi.org/10.1021/ja9107885

APA-Zitierstil: Gerbig, D., Reisenauer, H., Wu, C., Ley, D., Allen, W., & Schreiner, P. (2010). Phenylhydroxycarbene. Journal of the American Chemical Society. 132(21), 7273-7275. https://doi.org/10.1021/ja9107885