1.3.5- Trinitrobenzene visible spectrum

The reaction of 1,3,5-trinitrobenzene (TNB) and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene184 was also proposed to proceed by the mechanism shown in Scheme 16. The visible spectrum, recorded immediately after mixing appropriate solutions of TNB and DBU in toluene, shows a feeble absorbance maximum at 505 nm, which changes to a stable maximum at 468 nm, after variable reaction times. The first maximum was attributed to a molecular complex between TNB and DBU, and the second maximum at the Meisenheimer complex, 39, although NMR structural determinations were not possible, because of the low solubility of the complex in toluene. 

Solutions of 1,3,5-trinitrobenzene in methanol containing sodium methoxide are orange-coloured. The visible spectrum with maxima at... 

It is of interest that the visible spectrum of the Meisenheimer compound does not resemble the visible spectrum of either the product of reaction of s-trinitrobenzene with an alkoxide ion or the product resulting from the interaction of s-trinitrotoluene with an alkoxide ion. Moreover, these last two spectra do not resemble one another. The s-trinitrotoluene-alkoxide product has a spectrum similar to picrate ion. It shows a maximum at 370 m/t whereas picrate ion shows one... 

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