Author/Authors :
fawzy, a. assiut university - faculty of science - chemistry department, Assiut, Egypt , fawzy, a. umm al-qura university - faculty of applied science - chemistry department, Makkah, Saudi Arabia , el guesmi, n. umm al-qura university - faculty of applied science - chemistry department, Makkah, Saudi Arabia , el guesmi, n. faculté des sciences de monastir - département de chimie, Monastir, Tunisia , ali, h. m. aljouf university - faculty of science - chemistry department, Aljouf, Saudi Arabia , ali, h. m. assiut university - faculty of science - chemistry department, Assiut, Egypt , abdallah, m. benha university - faculty of science - chemistry department, Benha, Egypt , abdallah, m. umm al-qura university - faculty of applied science - chemistry department, Makkah, Saudi Arabia
Abstract :
Oxidation of tryptophan (Trp) by potassium permanganate in acid, neutral and alkaline media led to the formation of the corresponding aldehyde (indole-3-acetaldehyde), ammonia and carbon dioxide. The oxidation kinetics was studied by a spectrophotometric technique at fixed ionic strengths and ammonia and carbon dioxide. The oxidation kinetics was studied by a spectrophotometric technique at fixed ionic strengths and at 25 ᵒC. All the reactions showed a first order dependence on [MnO₄⁻] and fractional-first order kinetics in [Trp]. Fractional-second order kinetics in [H⁺] and fractional-first order dependence with respect to [OH⁻] were revealed in acid and alkaline media, respectively. An increase in the ionic strength in alkaline medium increased the oxidation rate of tryptophan, whereas it had a negligible effect on the oxidation rate in acid medium. Plausible oxidation mechanisms in all media were suggested and the rate-laws expressions were derived. Furthermore, the reactions constants included in the various steps of the suggested mechanisms were evaluated.
Keywords :
Tryptophan , Permanganate , Oxidation , Kinetics , Mechanism
