Catalytic Effect Of Cetyltrimethylammonium Bromide Research Articles

Micelle Catalyzed Oxidative Degradation of Paracetamol by Water Soluble Colloidal MnO2 in Acidic Medium

AbstractThe catalytic effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the MnO2-paracetamol (PCM) redox reaction has been examined spectrophotometrically in acidic medium at 298 K. The reaction demonstrates that the stoichiometric ratio of MnO2 and PCM is 1 : 1. The reaction exhibited first order kinetics with respect to [MnO2] and [PCM] but a negative fractional order was observed with respect to [H2SO4]. Various effects such as ionic strength, dielectric constant, [Mn(II)], [salts] and temperature have been studied. The catalytic effect of CTAB has been treated quantitatively by the well known Menger Portnoy and Piszkiewicz model. The values of binding constant (Ks), rate constant in the micellar phase (km), cooperativity index (n) and dissociation constant (KD) have also been calculated. From the several observations, a reaction mechanism has been proposed and the rate law has been derived. Applying the Arrhenius equation, various thermodynamic activation parameters have also been evaluated.

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 (Kobs), cooperatively index (n), binding constant (ks + ko), and corresponding activation parameters (Ea, ΔH#, ΔS#, and ΔG#) were determined. A suitable mechanism consistent with the experimental finding has been proposed.

Catalytic effect of CTAB on the interaction of dipeptide glycyl-tyrosine (Gly-Tyr) with ninhydrin

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of dipeptide glycyl-tyrosine (Gly-Tyr) with ninhydrin under varying conditions has been studied spectrophotometrically at 70°C and pH 5.0. The reaction followed first- and fractional-order kinetics with respect to [Gly-Tyr] and [ninhydrin], respectively. Increase in total concentration of CTAB from 0 to 70×10−3moldm−3 resulted in an increase in the pseudo-first-order rate constant (kψ) by a factor of ca. 3. Quantitative kinetic analysis of kψ−[CTAB] data was performed on the basis of pseudo-phase model of the micelles (proposed by Menger and Portnoy and developed by Bunton) and Piszkiewicz model. A possible mechanism has been proposed and the kinetic data have been used to evaluate the micellar binding constants KS (268mol−1dm3 for Gly-Tyr) and KN (64mol−1dm3 for ninhydrin).

Effect of Cetyltrimethylammonium Bromide on the Oxidation of Phthalic Acid by in Aqueous Medium

The conventional ultraviolet-visible (UV)-visible spectrophotometric technique was used to monitor the kinetics of the oxidation of phthalic acid by permanganate in absence and presence of cationic micelles of cetyltrimethylammonium bromide (CTAB). Under pseudo-first order conditions ([phthalic acid] ≥ ), the oxidation kinetics follows a complicate reaction path (the reaction rate decreases monotonically with [phthalic acid] which suggest the formation of more than one permanganate- phthalic acid complexes, out of these one of the complex has resistance toward the oxidative cleavage). The micellar catalysis is attributed to the formation of ion-pair between CTAB sub-aggregates and reactants as well as increase in the concentration (solubilization) of both reactants and/or intermediate in the micellar pseudo phase. The changes observed in the direction of the rate constants-[H+] profile correspond to the acid catalyses. The catalytic effect of CTAB may be due to the solubilization and incorporation of both the reactants into the Stern layer of the micelles and results have discussed in terms of pseudo-phase model of the micelles proposed by Menger and Portnoy and modified by Bunton et al. Mechanisms consistent with the observed kinetic data have been proposed. The effects of electrolytes, MnCl2, NaF, NaBr, and NaNO3, have also been studied and discussed. On the bases of observed results, a suitable mechanism has been proposed.

Kinetics of oxidation of d-glucose by permanganate in aqueous solution of cetyltrimethylammonium bromide

The catalytic effect of cetyltrimethylammonium bromide (CTAB) on the permanganate oxidation of d-glucose has been studied spectrophotometrically in presence of sulphuric acid. It was observed that the reaction proceeds in two stages (a slow step followed by a relatively fast second step). The influence of different parameters was measured i.e., [reactants], [surfactant], [sulphuric acid] and temperature. The absorbance of the reaction mixture increases with [CTAB] which suggests the association of permanganate with the cationic head group of CTAB. The effect of [surfactant] on the rate constants was explained in terms of the pseudo phase model proposed by Menger and Portnoy and modified by Bunton et al. On the basis of observed kinetic results, a suitable mechanism has been proposed.

Submicellar catalytic effect of cetyltrimethylammonium bromide in the oxidation of ethylenediaminetetraacetic acid by MnO 4−

The effects of cetyltrimethylammonium bromide (CTAB), sodiumdodecyl sulphate (SDS) and Triton X-100 (TX-100) on the oxidative degradation of ethylenediaminetetraacetic acid (EDTA) by MnO 4 − have been studied spectrophotometrically at 525 and 420 nm, respectively. It was found that cationic surfactant catalyse the reaction rate while anionic and non-ionic have no effect. The premicellar environment of CTAB strongly catalyses the reaction rate which may be due to the favorable electrostatic binding of both reactants (MnO 4 − and EDTA) with the positive head groups of the CTAB aggregates. The influence of different parameters such as [MnO 4 −], [EDTA], [H +] and [surfactants] were also considered. The reaction follows the first- and fractional-order kinetics with respect to [MnO 4 −] and [EDTA]. The proposed mechanism and the derived rate law are consistent with the observed kinetics.

Catalytic Effect of Cetyltrimethylammonium Bromide on the Oxidation of Triethylene glycol by Chloramine-T in Acidic Medium

The kinetics and mechanism of cetyltrimethylammonium bromide catalyzed oxidation of triethylene glycol [2,2'-ethylene diqxybis(ethanol)] by chloramine-T in acidic acid medium have been investigated. The reaction is first order dependence on chloramine-T and fractional order for triethylene glycol with excess concentration of other reactants. The catalytic effect due to cetyletrimethylammonium bromide has been studied. The small salt effect and increase in the reaction rate with increasing dielectric constant suggest the involvement of neutral molecule in the rate-determining step. The addition ofp-toluene sulfonamide retards the reaction rate. The effect of chloride ion on the reaction also studied. The effect of temperature on the reaction has been investigated in the temperature range 313-333K and thermodynamic parameters were calculated from the Arrhenious plot. A tentative mechanism consistent with the experimental results has been proposed.

Phosphorylation of alkylated poly(ethyleneimine) in chloroform in the presence of cetyltrimethylammonium bromide and calix[4]resorcinarene

The phosphorylation of alkylated poly(ethyleneimine) with 4-nitrophenyl bis(chloromethyl)phosphinate in chloroform in the presence of cetyltrimethylammonium bromide (CTAB), calix[4]resorcinarene (CR), or their mixture was studied by UV spectrophotometry. The catalytic effect of CTAB and CR on the process of polymer phosphorylation was shown to depend on the concentration of the surfactant and poly(ethyleneimine) in solution. The catalytic effect of the system is ascribed to the formation of poly(ethyleneimine)-CTAB, poly(ethyleneimine)-CR, and poly(ethyleneimine)-CTAB-CR mixed aggregates. Their existence was confirmed by the methods of light scattering and UV spectroscopy.

Catalytic effect of cetyltrimethylammonium bromide on the horseradish peroxidase-catalysed fluorogenic reaction between hydrogen peroxide and p-hydroxyphenylpropionic acid

A mechanistic study was made on the catalytic effect of cetyltrimethylammonium bromide (CTAB) on the horseradish peroxidase-catalysed fluorogenic reaction between para-substituted phenols and H 2O 2 with p-hydroxy-phenylpropionic acid as a model compound. The effect of CTAB was due to the interactions between the reaction products and the surfactant molecules. Novel behaviour of sodium chloride in the reaction was also observed.

Role of structural factors in micellar-catalyzed solvolysis of phosphonates

The catalytic effect of cetyltrimethylammonium bromide in the solvolysis of phosphonates depends on the nature of the substrate. The increase in reaction rate upon transition from water to the micellar phase is determined by the effectiveness of interaction of the phosphates with the micelles and by the region of their localization.

Catalytic effect of cetyltrimethylammonium bromide on the radical destruction oxidation of pyrocatechol violet

The effect of cetyltrimethylammonium bromide (I) on the radical oxidation of pyrocatechol violet by hydrogen peroxide was studied in the presence of N,N'-ethylenediamine-bis(o-aminobenzaldimine)cobalt(II) bromide and cobalt dichloride. After a short, faster period the reaction obeys the 1st order formalism. In the presence of I the experimental rate constants are as much as 42 times higher than in "pure" solutions. In optimum conditions (dye concentration 1.75 . 10-4 mol l-1) the reaction can be described in terms of the usual formalism of micellar catalysis. In solutions containing I the effect of cobalt compounds can be traced down to cobalt concentration levels of 10-8 mol l-1. The dependences of the experimental rate constants on the concentrations of hydrogen peroxide and cobalt compounds and on the temperature and pH are discussed.