Molecular structure of acetyl cyanide as studied by gas electron diffraction

The structure of acetyl cyanide has been determined by making joint use of the electron diffraction intensities measured in the present study and the rotational constants reported by Krisher and Wilson. The thermal average bond distances are: r_g(C-H) = 1.116±0.011 Å, r_g(CN) = 1.167±0.010 Å, r_g(CO) = 1.208±0.009 Å, r_g(C-C) = 1.477±0.008 Å and r_g(C-C _methyl) = 1.518±0.009 Å. The bond angles in the zero-point average structure ( r_av) are: ∠(C _methyl-CO) = 124.6±0.7°, ∠(C-C-C) = 114.2±0.9°, ∠(C-CN) = 179.2±2.2° and ∠(H-C-H) = 109.2±0.7°. The uncertainties represent the estimated limits of experimental error. The C-C single bond placed between the double and triple bonds is longer than those in vinylacetylene, acrylonitrile and propynal. Other structural parameters are also compared with those in related molecules. The infrared and Raman spectra of this molecule have been measured, and Urey-Bradley force constants have been determined.