Reinvestigation of the Structure of Dinitrogen Tetroxide, N2O4, by Gaseous Electron Diffraction

Abstract

A reinvestigation of the structure of N2O4 in the gas phase at −21 o C has given results in good agreement with an earlier study so far as the molecular shape is concerned, but the size of the molecule appears to be about 0.9% larger than originally thought. The results for the coplanar (D 2h symmetry) model are: r NN = 1.782 Å (0.0083), r NO = 1.190 Å (0.0018), ∠ ONO = 135.4 o (0.5 8 ), l NN = 0.0816 Å (0.0178), l NO = 0.0381 Å (0.0019), l o 1 o 2 = 0.0493 Å (0.0040), l N ··· O = 0.0729 Å (0.0061), l o 1 o 1′ = 0.0970 Å (0.0167), and l o 1 o 2′ = 0.0730 Å (0.0114). These distances and root‐mean‐square amplitudes are ra and la values; the parenthesized values are 2σ and include estimates of systematic error. The −NO2 groups have a structure very similar to that of NO2 itself. The very long N – N bond and its large amplitude of vibration imply a weak link and are in accord with the low dissociation energy.