ELECTRON-DIFFRACTION STUDY OF THE NITROGEN-DIOXIDE MOLECULAR-STRUCTURE AT 294, 480, AND 691 K

Gas-phase electron diffraction experiments have been carried out on NO 2 at three temperatures, viz,, 294, 480, and 691 K, Applying the neces sary vibrational corrections, the equilibrium structure (r(e)) of NO2 was determined from the 480 K data where it was the sole component of the vapor, 1.195(3) Angstrom and 133.7(2)degrees. This information was then utilized in the analysis of the mixture of NO2 (82%) and N2O4 (1 8%) at 294 K, The N-O bond of NO2 is shorter than that of N2O4 by 0.00 8 Angstrom, and the O-N-O angle opens slightly in the dimer as compare d with NO2. The barrier height to internal rotation in N2O4 is estimat ed to be about 40 kJ mol(-1) from the electron diffraction data. There is a slight increase of the average N-O bond length (r(g)) at higher temperatures. (C) 1997 Elsevier Science B.V.