Effect of Cationic Micellar Aggregates on the Kinetics of Dextrose Oxidation by N-Bromophthalimide

The effect of cationic micelles of Cetyltrimethyl ammonium bromide (CTAB) on the kinetics of oxidation of dextrose by N-Bromophthalimide were studied at 40°C. The reaction follows fractional-order and first order kinetics, with respect to [dextrose] and [NBP], respectively. CTAB strongly catalyze the reaction, and typical k_obs and [CTAB] profile was observed, that is, with a progressive increase in [CTAB], the reaction rate increased, reaches a maximum value then decreased. Results are treated quantitatively in terms of Berezin's Model, which is applicable to bimolecular micellar catalyzed reaction. There is a negative effect of mercuric acetate and phthalimide. The influence of salts on the reaction rates has also been seen. The activation parameters as well as other parameters were calculated and suitable mechanism consistent with the experimental findings has been proposed.

Keywords:

• Bimolecular reactions
• cationic micelles
• cetyltrimethyl ammonium bromide
• critical micellar concentration
• dextrose
• kinetics
• micellar catalysis
• N-bromophthalimide oxidation

Y. R. K. thanks the University Grants Commission, New Delhi for the Research Project Grant. Appreciation is also extended to Professor Laurence S. Romsted, Department of Chemistry, Wright–Rieman Laboratories, New Jersey (USA) for valuable discussions and fruitful suggestions.

Notes

Reaction conditions: [Hg(OAc)₂] = 5.0 × 10⁻⁴ mol dm⁻³; [CTAB] = 1.0 × 10⁻³ mol dm⁻³; Temperature = 40°C.

Literature value at 25°C is 9.2 × 10⁻⁴ mol dm⁻³.

Reaction conditions: Temperature = 40°C.

Reaction conditions: [NBP] = 2.0 × 10⁻⁴ mol dm⁻³; [Dextrose] = 5.0 × 10⁻² mol dm⁻³; [Hg(OAc)₂] = 5.0 × 10⁻⁴ mol dm⁻³; [CTAB] = 1.0 × 10⁻³ mol dm⁻³; acetic acid (45%)(v/v).

Reaction conditions: [NBP] = 2.0 × 10⁻⁴ mol dm⁻³; [Dextrose] = 5.0 × 10⁻² mol dm³ [Hg(OAc)₂] = 5.0 × 10⁻⁴ mol dm⁻³; Acetic acid (45%)(v/v).

Reaction conditions: [NBP] = 2.0 × 10⁻⁴ mol dm⁻³; [Dextrose] = 5.0 × 10⁻² mol dm⁻³; [Hg(OAc)₂] = 5.0 × 10⁻⁴ mol dm⁻³; [CTAB] = 1.0x10⁻³ mol dm⁻³; acetic acid (45%)(v/v).

^a Reaction conditions: [NBP] = 2.0 × 10⁻⁴ mol dm⁻³; [Dextrose] = 5.0 × 10⁻² mol dm⁻³.

[Hg(OAc)₂] = 5.0 × 10⁻⁴ mol dm⁻³; Acetic acid (45%)(v/v).

^b Reaction conditions: [NBP] = 2.0 × 10⁴ mol dm⁻³; [Dextrose] = 5.0 × 10⁻² mol dm⁻³; [Hg(OAc)₂ ] = 5.0 × 10⁻⁴ mol dm⁻³; [CTAB] = 1.0 × 10⁻³ mol dm⁻³; acetic acid (45%)(v/v).