Carbanion spectroscopy: cyanomethide anion (CH2CN-)

Autor:	Sean D. Moran, H. Benton Ellis, G. Barney Ellison, A. D. Mclean, D. J. Defrees
Rok vydání:	1987
Předmět:	Chemistry Ab initio General Chemistry Biochemistry Electron spectroscopy Catalysis Ion Crystallography Colloid and Surface Chemistry Computational chemistry Electron affinity Excited state Ionization energy Spectroscopy Carbanion
Zdroj:	Journal of the American Chemical Society. 109:5996-6003
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja00254a018
Popis:	The authors have measured the photoelectron spectra of CH/sub 2/CN/sup -/ and CD/sub 2/CN/sup -/ and report the following electron affinities: EA(CH/sub 2/CN) = 1.543 +/- 0.014 eV and EA(CD/sub 2/CN) = 1.538 +/- 0.012 eV. From an analysis of the peak splittings and intensities, they extract potential-energy curves for the umbrella mode of the CH/sub 2/CN/sup -/ negative ion and the CH/sub 2/CN radical. The radical is found to be a planar, C/sub 2v/ species. The structure of the cyanomethide ion is almost described as CH/sub 2/=C=N/sup -/, but the hydrogens are bent slightly out of the molecular plane. A Franck-Condon analysis leads to a value of the out-of-plane deformation angle as 30 +/- 5/sup 0/ with a very small inversion barrier of 100 +/- 50 cm/sup -1/. Their structural conclusions are reinforced by a series of ab initio Hartree-Fock and Moeller-Plesset perturbation calculations on both the cyanomethyl radical and cyanomethide ion. Using the gas-phase acidity of CH/sub 3/CN, they obtain the following bond-dissociation energy for acetonitrile: DH..pi../sub 298/ (H-CH/sub 2/CN) = 94.2 +/- 2.0 kcal/mol.
Databáze:	OpenAIRE
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