Medium effect on the reaction of N-n-butyl-2,4,6-trinitroaniline with NaOH.

MARÍA LAURA SALUM; RITA H. DE ROSSI; ELBA I. BUJÁN

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY

Wiley - VCH Verlag

Lugar: Weinheim; Año: 2007 vol. 2007 p. 2164 - 2174

1434-193X

The kinetics of the reaction of N-butyl-2,4,6-trinitroaniline (3) with NaOH have been studied in 10 and 60% 1,4-dioxane/H2O at 25ºC.  In both cases, several processes were observed.  In 10% 1,4-dioxane/H2O the only product formed was 2,4,6-trinitrophenol (4), whereas in 60% 1,4-dioxane/H2O a mixture of 4 and 5,7-dinitro-2--propyl-1H-benzimidazole 3-oxide (5) was observed in ratios that depend on the HO– concentration.   A mechanism involving the formation of s complexes by addition of one or two HO– anions to unsubstituted ring positions is proposed for 2,4,6-trinitrophenol formation.  The presence of these complexes was confirmed by NMR studies in 60% [D8] 1,4-dioxane/D2O. The mechanism suggested for the formation of the N-oxide includes the cyclization of an N-alkylidene 2-nitrosoaniline-type intermediate as the rate determining step.  The decrease in solvent polarity produces a decrease in the observed rate constant for the formation of 4 of about one order of magnitude making the cyclization reaction a competitive pathway.