title: Isoxazoles. VI: Aspects of the chemical stability of a new naphthoquinone-amine in acidic aqueous solution.
abstract: 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 acid 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 less than 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.
authors.affiliation: Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
authors.forename: M R
authors.initials: MR
authors.lastname: Longhi
authors.forename: M M
authors.initials: MM
authors.lastname: de Bertorello
mesh_terms: D002021:Buffers; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D002855:Chromatography, Thin Layer; D006863:Hydrogen-Ion Concentration; D007555:Isoxazoles / Q000032:analysis / Q000138:chemical synthesis*; D007700:Kinetics; D009285:Naphthoquinones / Q000032:analysis / Q000138:chemical synthesis*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D002021:Buffers; D007555:Isoxazoles; D009285:Naphthoquinones; D012996:Solutions; C066271:N-(3,4-dimethyl-5-isoxazolyl)-4-amino-1,2-naphthoquinone