DENSITY-FUNCTIONAL STUDY OF MOLECULAR-PROPERTIES OF HYDRAZOIC ACID AND METHYL AZIDE

Density functional calculations for hydrazoic acid HN3 and methyl azid e CH3N3 and for the respective singly ionized structures HN3+ and CH3N 3+ are reported. An analysis of the electrostatic solvent effects, bas ed on the self-consistent reaction field approach, on the molecular pr operties and conformational equilibrium of CH3N3 is also reported. The results are sensitive to the basis set quality and show some dependen ce on the different representations for the exchange-correlation funct ions. For HN3 very good agreement with experiment is observed for seve ral properties, such as the geometry, dipole moment, vibrational frequ encies and for the adiabatic first ionization energy. For CH3N3 the en ergy difference between eclipsed (ec) and staggered (st) conformers (d elta(ec-st)) is 2.5 kJ mol(-1), in good agreement with the experimenta l value (2.9 kJ mol(-1)), However, for CH3N3+, delta(ec-st) is -3.2 kJ mol(-1), reflecting a significant modification of the methyl group ro tational potential after ionization. Solvent effects on the molecular properties of CH3N3 are important when it is solvated in a polar mediu m. The most significant modifications concern the dipole moment and th e frequencies related to the CH3 symmetric stretch and torsion vibrati onal modes.