Carbanion Spectroscopy: ~CH₂NC

Photoelectron spectroscopy has been used to measure the electron affinities of the isocyanomethyl radicals: EA(CH2NC) = 1.059 ± 0.024 eV and EA(CD2NC) = 1.070 ± 0.024 eV. A Franck-Condon analysis of our spectra suggests that the isocyanomethide anion (”CH2NC) is a pyramidal species and a localized ion. This ion is bent out of the plane by 56 ± 5° with an inversion barrier of 650 ± 50 cm-1. These structural conclusions are examined by a series of ab initio Hartree-Fock and Moller-Plesset perturbation calculations on both the isocyanomethyl radical and isocyanomethide ion. Using the gas-phase acidity of CH3NC, we obtain the following bond-dissociation energy: DH0298(H-CH2NC) = 84.8 ± 3.1 kcal/mol. These results are used to compute the isomerization energies for “CH2NC —>° CH2CN“ and CH2NC —* CH2CN. These values are compared to other isocyano/cyano isomerizations. © 1987, American Chemical Society. All rights reserved.