Amines as Leaving Groups in Nucleophilic Aromatic Substitution Reactions. Part 5. Substitution vs. N-oxide formation in the reaction of N-n-butyl-2,6-dinitroaniline with hydroxide ion.

ELBA I. BUJÁN; A. IRENE CAÑAS; RITA H. DE ROSSI

Royal Society of Chemistry

Año: 2001 p. 1973 - 1973

kinetic study of the reaction of N-n-butyl-2,6-dinitroaniline 1 with NaOH was carried out in 10% 1,4-dioxane?water at 25 C, giving 2,6-dinitrophenol 2 and 7-nitro-2-n-propyl-1H-benzimidazole 3-oxide 3 in ratios depending on the HO- concentration. The rate constant for the formation of 2 is second order in HO concentration while that of 3 is first order then, the relative amount of 2 : 3 formed increases with HO. A mechanism involving the formation of a σ complex by addition of HO to an unsubstituted position of the aromatic ring is proposed for 2,6-dinitrophenol formation. The mechanism suggested for the formation of the N-oxide requires the deprotonation of the substrate.