87988-94-1Relevant academic research and scientific papers
Isoxazoles. 10. Degradation and enolization kinetics of 4- aminoisoxazolyl-1,2-naphthoquinone in basic aqueous solution
Ortiz,De Bertorello
, p. 783 - 785 (2007/10/03)
The kinetics of enolization and degradation of N-(5-methyl-4-isoxazolyl)- 4-amino-1,2-naphthoquinone (1) was investigated in aqueous solutions over a pH range of 7.30 to 12.25, at 35 °C and at constant ionic strength (μ = 0.5) using reversed-phase HPLC. Pseudo-first-order kinetics was observed throughout the pH range studied. The rate of enolization (k(e)), the keto- enol equilibrium constant (K(t)), and specific base catalysis rate constant (k(OH)) were determined. Good agreement between the theoretical pH-rate profile and the experimental data supports the proposed transformation process. The average recovery for 1 and its tautomerization product 2- hydroxy-N-(5-methyl-4-isoxazolyl)-1,4-naphthoquinone 4-imine (2) from mixtures of different composition was evaluated.
Isoxazoles. 9. Degradation kinetics of 4-(isoxazolylamino)-1,2- naphthoquinone in acidic aqueous solution
Ortiz,De Bertorello
, p. 1457 - 1460 (2007/10/02)
The degradation kinetics of N-(5-methyl-4-isoxazolyl)-4-amino-1,2- naphthoquinone (1) was studied in aqueous solution over a pH range of 0.65- 7.50, at 35 °C and at a constant ionic strength of 0.5. The degradation rates were determined by high-pressure liquid chromatography and were observed to follow pseudo-first-order kinetics with respect to the concentration of 1. The pH-rate profile was linear with slope -1 under acidic pH, becoming pH independent from 3.50 to 7.50. Good agreement between the theoretical pH-rate profile and the experimental data supports the proposed degradation process. The catalytic rate constants for hydrogen ion and water were k(H) = 0.901 M-1 h-1 and k(o) = 1.34 x 10-3 h-1, respectively. These data are appropriate to develop a stable dosage form of 1. The accuracy, peak sharpness, and asymmetry factor for the analytical method were determined.
