Infrared studies of the 1,3,5-trinitrobenzene – cyanide ion complex

Abstract

Quantitative infrared studies have been made of the interactions of 1,3,5-trinitrobenzene and 1,3,5-trinitrobenzene-d, with cyanide ion in chloroforn~, deuterochloroform, and acetonitrile. Absorption bands assignable to the 1 :1 complex have been characterized and attempts made to assign the absorptions to fundamental modes of the complex.

Anionic sigma complexes

“…These reach maximum intensity at a 1:1 equivalent ratio of 1,3,5-TNB:cyanide and are attributed to the asymmetric and symmetric N02 stretching modes of 6g. 189 The same changes occur when cyanide is added to a solution of l,3,5-TNB-rf3 in chloroform. 189 The complex 6g also has an absorption at 1495 cm-1 which might be assigned to the asymmetric N02 stretch analogous to the assignment made for 19a.192 '193 The extinction coefficient of this peak is much smaller than would be expected for N02 vibrations, however, and the 1235-cm-1 band is thus a more likely assignment.…”

“…192 The absorption at 1492 cm-1 could result from a ring vibration, however.198 In 1,3,5-TNB, the asymmetric and symmetric N02 absorptions appear at 1550 and 1345 cm-1, with extinction coefficients (chloroform) of 1740 and 1400 M-1 cm-1, respectively. 189 In addition, a symmetric N02 deformation appears at 825 cm-1, an in-plane bending vibration at 518 cm-1, and an in-plane rocking vibration at 360 cm-1. 189 When cyanide is added to a chloroform solution of 1,3,5-TNB, both the symmetric and asymmetric N02 absorptions diminish as two new peaks with similar extinction coefficients appear at 1235 and 1190 cm-1.…”

“…189 In addition, a symmetric N02 deformation appears at 825 cm-1, an in-plane bending vibration at 518 cm-1, and an in-plane rocking vibration at 360 cm-1. 189 When cyanide is added to a chloroform solution of 1,3,5-TNB, both the symmetric and asymmetric N02 absorptions diminish as two new peaks with similar extinction coefficients appear at 1235 and 1190 cm-1. These reach maximum intensity at a 1:1 equivalent ratio of 1,3,5-TNB:cyanide and are attributed to the asymmetric and symmetric N02 stretching modes of 6g.…”

Resonance Raman investigation of meisenheimer complexes derived from 1,3,5‐trinitrobenzene

“…Fortunately, for the spectra excited by the lines at 457. 9 and 488.0 nm, the fluorescence level was low enough to allow reliable and reproducible spectra to be obtained. Consequently, it was only possible to investigate the resonance behaviour with respect the more energetic electronic transitions.…”

Janovsky reactions between cyclopentadienyliron complexes of substituted benzenes and carbanions derived from ketones

“…It is of interest to note that in Meisenheimer or Janovsky type of adducts of nitroarenes such as 1,3,5-trinitrobenzene, from the ir spectra, it was found that there was a lowering of the asymmetric and symmetric stretching vibrational frequencies of the NO2 group when compared with the analogous frequencies in the nitroarene, and this finding was attributed to a decrease in the N-0 bond order because of the transfer of negative charge to the nitro groups in the adduct (15,16).3 A similar lowering in NO2 stretching frequencies was observed in the presently prepared Janovsky adducts; for example, the ir frequencies for the NO2 group of 2 a are lower than the corresponding frequencies for the NO2 group of cation l a (Table 2) from which 2 a was prepared. Apparently, such a decrease in bond order also occurred in the CN, SO2, or CO substituent directly attached to the complexed cyclohexadienyl ligand in adduct 2b, 2c, or 2d, with the corresponding ir absorptions in cation l b , l c , or I d , respectively, appearing at higher frequencies (Table 2).…”