Isoxazoles VI. Aspects of the Chemical Stability of a New Naphthoquinone-amine in Acidic Aqueous Solution.

LONGHI MARCELA, AND BERTORELLO MARÍA.

JOURNAL OF PHARMACEUTICAL SCIENCES

John Willey & Sons

Lugar: New York, USA.; Año: 1990 vol. 79 p. 754 - 757

0022-3549

Some aspects of the chemical degradation of N-(3,4-dimethyl-5-isoxazolyl)-4-amino-1,2-naphthoquinone were investigated as a function of pH and temperature. In acidic and neutral pH, four main degradation products were identified: 2-hydroxy-1,4-naphthoquinone, 2-butanone, ammonia, and hydroxylamine. No significant buffer effects were observed for the buffer species used in this study. The pH-rate profile exhibited a specific acid catalysis which is important at pH values <3.5, and an inflection point at pH 1.10 corresponding to a pKa value. From Arrhenius plots, the activation energy was found to be 17.8 ± 0.3 kcal/mol.