Inhibition Effect of {Cationic Surfactant-Ascorbic Acid} Premicellar Aggregation on the Rate of Hexacyanoferrate(III) Oxidation of Ascorbic Acid: A Kinetic Study

Abstract

The kinetics of oxidation of ascorbic acid by acidic hexacyanoferrate(III) have been investigated in presence of cationic surfactant viz. cetyltrimethylammonium bromide (CTAB). An inhibition effect of CTAB (below its critical micelle concentration) on the rate of oxidation has been observed. The spectrophotometric and kinetic data support a 1:1 premicellar association between substrate and surfactant. A mechanism has been proposed and a rate law consistent with kinetic results has been derived.

Keywords:

• Ascorbic acid
• cetyltrimethylammonium bromide
• hexacynoferrate (III)
• Kinetics of oxidation

The work is part of FAST TRACK Scheme in young scientist category awarded to Neelu Kambo.

Notes

[] = 10 × 10⁻⁴ mol dm⁻³, [HClO₄] = 0.4 mol dm⁻³, [CTAB] = 1.37 × 10⁻⁵ mol dm⁻³.

[Fe(CN)₆ ⁻³] = 10 × 10⁻⁴ mol dm⁻³, [HClO₄] = 0.4 mol dm⁻³, [AH₂] = 10 × 10⁻⁴ mol dm⁻³.