Theoretical calculations of chemical interactions. Part 5. 1,1-Disubstituted 2,4,6-trinitrocyclohexadienylide (‘Meisenheimer’) complexes

Abstract

All-valence-electron MNDO SCF-MO calculations with almost complete geometry optimization have been performed on 1,1-dimethoxy-2,4,6-trinitrocyclohexadienylide. The computed geometrical parameters have been compared with X-ray data. Charge distributions have been calculated for this complex and for 2,4,6-trinitroanisole, and the differences in electron densities for each atom compared with the ¹H and ¹³C n.m.r. chemical shifts for both compounds. Similar calculations have been performed for 1,1-difluoro-2,4,6-trinitrocyclohexadienylide and for picryl fluoride. The results have been compared with available ¹H n.m.r. data. The reasonable good agreement between calculated and experimental data indicates that for these systems the MNDO method can be safely used to calculate properties of species not yet amenable to experiment.