Effect of Anionic Surfactant on the Oxidation of DL-Aspartic Acid by N-Bromophthalimide: A Kinetic Study

Abstract

The kinetics of oxidation of DL-Aspartic acid (Asp) by N-bromophthalimide (NBP) was studied in the presence of sodium dodecyl sulfate (SDS) in acidic medium at 308 K. The rate of reaction was found to have first-order dependence on [NBP], fractional order dependence on [Asp] and inverse fractional order dependence on [H⁺]. The addition of reduced product of the oxidant, that is, [Phthalimide] has decreased the rate of reaction. The rate of reaction increased with increase in inorganic salts concentration, whereas a change in [Cl⁻], ionic strength of the medium and [Hg(OAc)₂] had no effect on the oxidation velocity. The rate of reaction decreased with a decrease in dielectric constant of the medium. COOH-CH₂-CN was identified as the main oxidation product of the reactions. The various activation parameters have been computed. A suitable reaction mechanism consistent with the experimental findings has been proposed. The micelle-binding constant has been calculated.

Keywords:

• Anionic surfactant
• DL-aspartic acid
• kinetics
• N-bromophthalimide
• oxidation

Acknowledgments

Y. R. Katre and G. K. Joshi thank the University Grants Commission, New Delhi for Minor Research Project & Rajiv Gandhi National Research Fellowship, respectively.

Notes

Solution conditions: [NBP] = 1 × 10⁻⁴ mol dm⁻³, [Asp] = 1 × 10⁻³ mol dm⁻³, [H⁺] = 5 × 10⁻³ mol dm⁻³, [SDS] = 8.3 × 10⁻³ mol dm⁻³, [Hg⁺⁺] = 2 × 10⁻⁴ mol dm⁻³, CH₃COOH = 50%.

Solution conditions: [NBP] = 1 × 10⁻⁴ mol dm⁻³, [Asp], [Ser], and [Ala] = 1 × 10⁻³ mol dm⁻³, [Gly] = 5 × 10⁻⁴ mol dm⁻³, [H⁺] = 5 × 10⁻³ mol dm⁻³, [SDS] = 8.3 × 10⁻³ mol dm⁻³, [Hg⁺⁺] = 2 × 10⁻⁴ mol dm⁻³, CH₃COOH = 50% and (40% for [Gly]).

^a Literature value for SDS at 25 °C = 8.1 × 10⁻³ mol dm⁻³. Solution conditions: [NBP] = 1 × 10⁻⁴ mol dm⁻³, [Asp] = 1 × 10⁻³ mol dm⁻³, [Hg⁺⁺] = 2 × 10⁻⁴ mol dm⁻³, [H⁺] = 5 × 10⁻³ mol dm⁻³, [SDS] = 8.3 × 10⁻³ mol dm⁻³, [CH₃COOH] = 50%.