Kinetics and Mechanism of Cetyltrimethylammonium Bromide Catalyzed N-Bromosuccinimide Oxidation of D-Mannose in Acidic Medium

The kinetics and mechanism of N-bromosuccinimide (NBS) oxidation of D-mannose in the absence and presence of cetyltrimethylammonium bromide (CTAB) in acidic media have been studied under the condition [D-mannose]_T ? [NBS]_T at 40°C. Under the kinetic conditions, both the slower uncatalyzed and faster catalyzed paths go on. Both the paths show the fractional and first order dependence on [D-mannose] and [NBS]_T, respectively. The rate decreased with increase in acidity. Neither succinimide (NHS) nor Hg(II) influenced the reaction rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50°C). The influence of salts on the reaction rate was also studied. CTAB accelerates the reactions and the observed effects have been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. In the reaction, approximately 1 mole of NBS oxidized one mole of D-mannose. A reaction scheme of the oxidation of D-mannose by NBS was found to be in consistent with the rate law and the reaction stoichiometry.     

Kinetics and mechanism of oxidation of β-Alanine by <Emphasis Type="Italic">N</Emphasis>-bromophthalimide in the presence of Ru(III) chloride as homogenous catalyst in acidic medium

The kinetics of Ru(III) chloride-catalyzed oxidation of β-Alanine (NH₃ ⁺CH₂CH₂COOH, β-Ala) by N–bromophthalimide (NBP) in aqueous perchloric acid medium was studied at 35 °C. The rate law followed a first-order and zero-order dependence with respect to [NBP] and [β-Ala], respectively. The reaction followed first-order kinetics with respect to [Ru(III)] chloride at a range of low concentrations while the order changed from first- to zero-order at high concentration of [Ru(III)] chloride; demonstrating the catalytic effect for the oxidation of β-Ala by NBP. The rate decreased with increase in acidity. Chloride ions positively influenced the rate of the reaction. Neither phthalimide (NHP) nor Hg(II) influenced the reaction rate. Ionic strength (I) and dielectric constant (D) of the medium had no significant effect on the rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50 °C). The colorimetric, FTIR, and GC-MS techniques were used to identify methyl cyanide (CH₃CN) and CO₂ as products of the reaction. In the reaction, approximately 2.3 moles of NBP oxidized one mole of β-Ala. A reaction scheme of the oxidation of β-Ala by NBP in the presence of Ru(III) chloride was found to be in consistent with the rate law and the reaction stoichiometry.     

Kinetic study of the ruthenium(III)-catalyzed oxidation of glycine by <Emphasis Type="Italic">N</Emphasis>-bromophthalimide in acidic medium

The kinetics of ruthenium(III) chloride-catalyzed oxidation of glycine by N–bromophthalimide (NBP) was studied in aqueous perchloric acid at 35 °C. The results showed first- and zero-order behavior with respect to NBP and Gly, respectively. Ru(III) showed a catalytic effect on the reaction which followed first-order kinetics with respect to [Ru(III)] at a low concentration range and tended to zero order at high concentration range. The rates decreased with increase in the proton concentration, while chloride positively influenced the rate of the reaction. Two moles of NBP were required to oxidize one mole of Gly, and the products were identified as phthalimide (NHP), HCN, CO₂, and Br⁻. Neither added NHP nor Br⁻ influenced the reaction rate. Ionic strength and dielectric constant of the medium had no significant effect on the rate. Activation parameters were determined by studying the reaction at different temperatures. A reaction scheme of the catalytic oxidation is proposed.     

Kinetic study of oxidation of galactose by N-bromo phthalimide in the presence of cationic micelle in acidic medium

The kinetics of micellar catalyzed oxidation of galactose by N-bromophthalimide was studied in the presence of acidic medium at 308?K. The oxidation reaction exhibits first-order kinetics with respect to oxidant (N-bromophthalimide), fractional order with respect to substrate (galactose) and positive fractional order with respect to HClO₄ on the rate of reaction. The rate of the reaction increased with decreasing the dielectric constant of the medium. With a progressive increase in the concentration of CTAB, the rate of reaction increased and after reaching peak k _obs, decreased at higher concentrations of CTAB. There catalytic roles are best explained by Berezin??s model. The influence of salts on the reaction rate was also studied. The various activation parameters have been calculated. The rate constant and binding constant with the surfactant have also been evaluated. A suitable mechanism consistent with the experimental findings has been proposed.     

Kinetics and mechanism of oxidation reaction of lactose by N-bromophthalimide: Micelles used as a catalyst

The kinetics and mechanism of the oxidation of lactose by N-bromophthalimide in the absence and presence of cetyltrimethylammonium bromide and sodium dodecyl sulfate micelles was investigated in the presence of sulfuric acid medium. Under pseudo-first-order conditions reaction rate agreed with a first-, fractional- and negative fractional-order kinetics in N-bromophthalimide, lactose and sulfuric acid, respectively. In the presence of additives, the critical micellar concentration values were lower than those given in the literature. The catalytic role of cationic micelles was explained by the Berezin model. The anionic micelles showed slightly inhibitory effect. The influence of salts, phthalimide and mercuric acetate on the reaction rate was also studied. Using the kinetic data, the rate constant, binding constants, and corresponding activation parameters were evaluated. A possible reaction mechanism, which is based on the kinetic results and the product analysis, is proposed.     

硫酸存在时N-溴代苯二甲酰亚胺对甘露糖的胶束催化氧化

The kinetics of micellar-catalyzed oxidation of mannose by N-bromophthalimide was studied in the presence of sulfuric acid at 313 K. The orders of reaction with respect to [mannose], [oxidant], and [H+] were found to be fractional, first, and negative fractional order, respectively. Anionic micelles of sodiumdodecyl sulfate showed a partial inhibitory effect, while cationic micelles of cetyltrimethylammonium bromide increased the reaction rate with the same kinetic behavior. The reaction was catalyzed by cationic micelles, because of favorable electrostatic/thermodynamic/hydrophobic/hydrogen bonding between reactants and cationic micelles. Their catalytic roles are best explained by Berezin’s model. A variation of [phthalimide] showed that the rate of reaction decreased with increasing [phthalimide]. It was observed that, an increase of [mercuric acetate] had no effect on reaction velocity. The influence of salts on the reaction rate was also studied. The rate constant (kW ), binding constants (KS+KO), and corresponding activation parameters (Ea, ⊿H#, ⊿S#, and ⊿G#) were determined. A detailed mechanism with associated reaction kinetics is presented and discussed.     

Catalytic Effect of Cetyltrimethylammonium Bromide on the Oxidation of Oxalic Acid by N-Bromophthalimide in Acidic Medium

The kinetics of micellar catalyzed oxidation of oxalic acid [OA] by N-bromophthalimide was studied in the presence of perchloric acid at 308 K. The orders of reaction with respect to [Oxalic acid], [oxidant], and [H⁺] were found to be fractional, first and negative fractional order respectively. Cationic micelles of cetyltrimethylammonium bromide increased the reaction rate. The effect of phthalimide, mercuric acetate and inorganic salts, that is, [Cl^?][Br^?] has also been done. The rate reaction decreases with increasing dielectric constant of the medium. The results are treated quantitatively in terms of Piszkiewicz and Berezin models. The rate constant (K_obs), cooperatively index (n), binding constant (k_s + k_o), and corresponding activation parameters (E_a, ΔH^#, ΔS^#, and ΔG^#) were determined. A suitable mechanism consistent with the experimental finding has been proposed.     

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.