Near Ultraviolet Absorption Spectra of Halogenated Nitrobenzenes

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ3,2-benziodaoxol-3-one

“…In contrast, the nitrated product 3 exhibits a maximum λ max = 236 nm (ε = 8.9 × 10 3 M −1 cm −1 ) and features a broad sideband ranging from 260 nm (ε = 8.0 × 10 3 M −1 cm −1 ) up to 350 nm, hence accounting for its pale yellow coloration. Generally, these observations are in line with data reported on the analogous pair of iodobenzene and 1-iodo-4-nitrobenzene [ 13 – 14 ]. However, whereas the broad sideband in 1-iodo-4-nitrobenzene is usually observed around 300 nm, a strong hypsochromic shift of roughly 40 nm is observed for 3 .…”

Light Absorption Studies: Part Xi Electronic Absorption Spectra of Nitrobenzenes

“…12), it follows that in the absence of other considerations the nitro-group would be expected to exert a greater negative mesomeric interaction than the acetyl-group and in this way nitrobenzene absorbs a t longer wavelength. I t may be noted that the large mesomeric effect of the nitro-group can be used t o explain the large frequency shift of the C-H bending vibration in nitrobenzene ( 1 3 ) , and also the extremely high intensity of the R-KO2 stretching vibration (8f) and the enhanced intensities of the aromatic bands a t 1600-1500 cm-I for nitrobenzenes (8b), since absorption intensities in the infrared region are probably largely proportio~lal t o resonance interaction (14,15).…”

Light-Absorption Studies: Part X. Ultraviolet Spectra in Acid and Basic Media–—some Further Observations on the Ortho Effect

“…'This is in fact indicated since the order for the halogens in their short-range interactions sometimes suggests the order of the inductive effects. For example, Ungnade (23) reports an order of -F > -C1 > -Br > -I for the negative wave-length displacements relative to nitrobenzene. However, the inductive effect does not fully explain many of the wavelength displacements caused by the short-range interaction and hence it is preferable to consider the over-all electronegativity independently for each set of examples (15).…”