Knowledge Bank

The infrared spectrum in the 2 to 35 micron region has been obtained for dinitrogen pentaoxide. The infrared data and the available Raman data are consistent with the $O2N-O-NO2$ structure for the molecule, although the relative orientation of the two nitro groups is not certain. Spectral data and entropy calculations indicate that the frequency of the N--O--N angle deformation mode will probably be less than $200cm-1$. Comparison of the vapor spectrum to the solid spectrum and the temperature dependence of the solid spectrum suggest that in the vapor phase there is little potential barrier against internal rotations of the nitro groups. An approximate normal coordinate analysis has also been made assuming several possible structures and using the Urey-Bradley type potential field.