Kinetics and mechanism of spiro adduct formation from and smiles rearrangement of N-methyl-N-(2,4,6-trinitrophenyl)aminoacetanilide. Base-catalyzed transformation of N-(2,4,6-trinitrophenylamino)acetanilide into 2-nitroso-4,6-dinitroaniline

Abstract

The paper deals with kinetics and mechanism of the reaction of N-(2,4,6-trinitrophenyl)aminoacetanilide (IIa) with methoxide ion and with the reaction kinetics and product structure of the reaction of N-methyl-N-(2,4,6-trinitrophenyl)aminoacetanilide (IIb) in methanolic buffers. The main product of the reaction of compound IIa with methoxide is 2-nitroso-4,6-dinitroaniline along with about 3% spiro adduct. The dependence of the experimental rate constant kexp of the reaction with methoxide on the methoxide concentration is similar to that of the reaction of N-(2,4,6-trinitrophenyl)glycine methylamide, however, compound IIa reacts about 2·5 times faster and produces the spiro adduct in an about four times smaller amount. In basic acetate buffers, compound IIb is transformed quantitatively into the spiro adduct. In chloroacetate buffers, the reverse ring opening of the spiro adduct prevails. The ring opening takes two ways: A specific acid catalyzed one and a non-catalyzed one. Corresponding therewith is the non-catalyzed and specific base catalyzed formation of the spiro adduct. In aniline-anilinium chloride buffers, equilibrium is rapidly established between the spiro adduct and 2-methylamino-N-phenyl-N-(2,4,6-trinitrophenyl)acetamide hydrochloride. The mixture of the two compounds is transformed gradually into compound IIb which shows the highest thermodynamic stability in the given medium. At [H+] > 10-3 mol l-1 the thermodynamically most stable species is 2-methylamino-N-phenyl-N-(2,4,6-trinitrophenyl)acetamide hydrochloride.