Characterization of C-NO2 Bonds in Nitroaromatic Compounds: A Bond Disproportionation Approach

Homolytic dissociation of C-NO2 bond represents the primary fission process of nitroaromatic compounds under thermal, impact, shock and electric spark initiation stimuli. Homolytic bond dissociation energies BDE(C-NO2) describe the C-NO2 bond fission. Theoretical calculations of BDEs are substantially influenced by inadequate treatment of electron correlation. Recently the alternative method was suggested to overcome this substantial drawback - an isodesmic reaction RC-NO2 + SC-H -> RC-H + SC-NO2 where SC-NO2 is standard nitroaromatic compound. This reaction is characterized by bond disproportionation energy DISP(C-NO2), which inherently cancels the electron correlation effect accompanying homolytic bond dissociation energies. The bond disproportionation energies DISP(C-NO2) and bond dissociation energies BDE(C-NO2) were evaluated for 11 nitro benzenes and 19 nitro toluenes at DFT B3LYP/6-311+G(d,p) level and correlated with their detonation velocities, D, and with charge of the most reactive nitro group, Q(NO2).