Structure and vibrational spectra of dinitromethane and trinitromethane

The molecular geometries of dinitromethane and trinitromethane were optimized and their harmonic force fields were calculated by the DFT/B3LYP method. The force fields obtained made it possible to interpret reliably the vibrational spectra of dinitromethane, trinitromethane and a number of isotopomers of trinitromethane. Some general conclusions on geometry and vibrational spectra of the molecules under study are made. The hybrid density functional method used is shown to predict the reliable structural parameters and vibrational frequencies for polynitromethanes.