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

 

Michal PEXA and Zdeněk FRIEDL
Faculty of Chemistry, Brno University of Technology
Purkyňova 118, 612 00 Brno, Czech Republic


Abstract: Homolytic dissociation of C-NO2 bond represents the primary fssion
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 fssion. Theoretical calculations of BDEs are substantially
infuenced 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).

Keywords: bond dissociation energy, bond disproportionation energy, nitro
benzenes, nitro toluenes, detonation velocity