Calculation of the Average Structure of Ethylene

The average structure of ethylene in the ground vibrational state has been calculated from the internuclear distances (rg) obtained from electron diffraction by making corrections for the effect of atomic displacements perpendicular to the equilibrium bond directions and the centrifugal distortion, and from the rotational constants A0, B0, and C0 obtained from infrared and Raman spectra by making corrections for the interactions of vibration and rotation. Good agreement is observed between the diffraction and spectroscopic average structures, and the following average structure of C2H4 has been determined: rz(C=C) = 1.335±0.003 Å, rz(C–H) = 1.090±0.003 Å, and ∠zC–C–H = 121.7°±0.4°.