Medium Effect on the Reaction of N-butyl-2,4,6-trinitroaniline with NaOH

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

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY

Wiley- InterScience

Año: 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 25 °C. 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-benzimidazole3-oxide (5) was observed in ratios that depend on the HO? concentration. A mechanism involving the formation of σ complexes through the addition of one or two HO? anions to unsubstituted ring positions is proposed for 2,4,6-trinitro-phenol 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.