Cationic Surfactant N-cetylpyridinium Chloride Research Articles

Determination of the activation parameters ∆H≠ and ∆S≠ via a kinetic study of d,l-mandelic acid oxidation by using chromic acid in the presence of 1,10-phenanthroline as a promoter in an aqueous micellar acid medium

Chromic acid oxidation of d,l-mandelic acid in the presence and absence of 1,10-phenanthroline (Phen) is studied in an aqueous micellar medium under kinetic conditions, [d,l-mandelic acid] >> [Phen]T >> [Cr(VI)]T at different temperatures. From studies on the effect of temperature on the rate constant (k), the activation parameters ∆H≠ (enthalpy of activation) and ∆S≠ (entropy of activation) are evaluated by using the Eyring equation [−ln (kh/kBT) = ∆H≠/RT − ∆S≠/R]. The high value of ∆H≠ indicates that the phen-catalysed path is favoured mainly due to very high negative value of ∆S≠. The negative value of ∆S≠ and the composite rate constant kcat support the suggested cyclic transition state. Both the catalysed and uncatalysed paths show a first-order dependence on [H+], and both also show a first-order dependence on [d,l-mandelic acid]T and [Cr(VI)]T. The Phen-catalysed path is first order in [Phen]T. These observations remain unaltered in the presence of externally added surfactants. The cationic surfactant N-cetylpyridinium chloride is found to retard the rate of the reaction.

Analysis of Techniques for Improving the Adsorption Capacity of Talc

Mineral adsorbents, such as talc, are materials that are abundant in nature and used as scavengers, binding agents, fillers, etc. Mechanical and physicochemical pretreatment creates new opportunities for the production of highly effective mineral materials with a wide range of destinations. The possibility of using various techniques to enhance the adsorption properties of dispersed talc, namely, enrichment and use in a mixture with another mineral, treatment with various reagents, and changing the temperature and acidity conditions, is demonstrated. Phenomena and trends having an effect on the adsorption ability of talc are considered. Surface modification of talc can significantly increase its technological capability of absorbing resinous components of wood pulp in the manufacture of paper. It is shown that the adsorption and structural characteristics of dispersed talc change significantly after modifying it with organic reagents. The best effect is achieved when pretreating talc with cationic surfactant N-cetylpyridinium chloride. The resulting adsorbent is characterized by a high value of rosin adsorption, reaching 200 mg/g, which is commensurate with the data on the absorption of rosin by talc pretreated with a Penta-416 industrial mixture. Substantial changes in the surface properties due to an increase in the temperature, a change in the acidity, and a shift in the hydrophilic-hydrophobic balance occur when using the accessible, affordable, and safe anionic surfactants. The highest value of adsorption of rosin (160–170 mg/g) is typical for samples of talc modified with sodium oleate and enriched with zinc oxide. The importance of pretreatment of talc with solutions of mineral acids and salts that promote settling of suspensions and the formation of a compact precipitate is shown.

Optimal Process Condition for Room Temperature Hetero-Aromatic Nitrogen Base Promoted Chromic Acid Oxidation of p-Chlorobenzaldehyde to p-Chlorobenzoic Acid in Aqueous Micellar Medium at Atmospheric Pressure

Abstract The present paper describes the kinetics of oxidation of p-chlorobenzaldehyde by chromic acid in aqueous and surfactant media in the presence of a promoter at 303 K. The rate constants were found to increase with introduction of hetero-aromatic nitrogen base promoters such as picolinic acid (PA), 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen). The product p-chlorobenzoic acid has been characterized by NMR. The mechanism of both unpromoted and promoted reaction paths has been proposed. In presence of the anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant N-cetylpyridinium chloride (CPC) and non-ionic surfactant Triton X-100 (TX-100) the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation. Both SDS and TX-100 produce a normal micellar effect whereas CPC produces a reverse micellar effect in the presence of p-chlorobenzaldehyde.

Combination of Best Promoter and Micellar Catalyst for Chromic Acid Oxidation of D-Arabinose in Aqueous Media at Room Temperature

AbstractThe present paper describes the kinetics and mechanism for oxidation of D-arabinose by Cr(VI) in the presence of a micellar media. The anionic surfactant sodium dodecyl sulphate (SDS) and nonionic surfactant Triton-X-100 (TX-100) accelerate the process while the cationic surfactant N-cetylpyridinium chloride (CPC) retards the reaction. A suitable mechanism has been proposed. The reaction constants involved in different steps of the mechanism have been calculated. Formic acid and erythronic acid were reported as the products of oxidation of the sugar.

Micellar Catalysis on 1,10-Phenanthroline Promoted Chromic Acid Oxidation of Dimethyl Sulfoxide to Dimethyl Sulfone in Aqueous Media at Room Temperature

The monomeric species of Cr(VI) was found to be kinetically active in the absence of 1,10-phenanthroline (phen) under pseudo-first order conditions, whereas in the 1,10-phenanthroline promoted path, the Cr(VI)-phenanthroline complex undergoes a nucleophilic attack by dimethyl sulfoxide (DMSO) to form a ternary complex which subsequently undergoes a redox decomposition leading to dimethyl sulfone and Cr(III)-phenanthroline complex. A detailed study was done to investigate the effect of cationic surfactant N-cetylpyridinium chloride (CPC), anionic surfactant sodium dodecyl sulphate (SDS) and neutral surfactant (TX-100) on the phen promoted chromic acid oxidation of DMSO in aqueous media at 30°C. The aggregation and morphology of the micelles formed by the surfactants were studied by optical microscope and Transmission Electron Microscope (TEM). 1,10-phenanthroline in association with SDS micelle exhibited almost 70-fold rate enhancements compared to the uncatalyzed reaction path.

Combination of Best Promoter and Micellar Catalyst for Cr(VI) Oxidation of Lactose to Lactobionic Acid in Aqueous Medium at Room Temperature

AbstractIn aqueous acidic media, picolinic acid, 2,3-dipicolinic acid, and 2,6-dipicolinic acid promoted Cr(VI) oxidation of lactose to lactobionic acid has been carried out at room temperature. A possible reaction mechanism, which is based on the kinetic results and the product analysis, has been proposed. The anionic surfactant sodium dodecyl sulphate (SDS) and nonionic surfactant Triton-X-100 (TX-100) accelerate the process while the cationic surfactant N-cetylpyridinium chloride (CPC) retards the reaction.

Rate enhancement via micelle encapsulation for room temperature metal catalyzed Ce(IV) oxidation of p-chlorobenzaldehyde to p-chlorobenzoic acid in aqueous medium at atmospheric pressure

The kinetics and mechanism of the Ru(III) and Ir(III) catalyzed oxidation reaction of p-chlorobenzaldehyde by ceric(IV) have been studied spectrophotometrically at constant ionic strength of 2.0moldm−3 in the presence and absence of the cationic surfactant N-cetylpyridinium chloride (CPC) at 30°C. The oxidized product p-chlorobenzoic acid was confirmed by the 1H NMR, HR Mass and FTIR spectral analysis. Dramatic rate enhancements have been observed in the oxidation of p-chlorobenzaldehyde by ceric(IV) in the presence of metal ions Ru(III) and Ir(III). The rate of oxidation in the presence of catalyst Ru(III) is much faster than in the Ir(III) catalyzed reaction in micellar media. The observed micellar effect is explained on the basis of reverse CPC micelle formation. This phenomenon was identified with the help of UV Spectra and Scanning Electron Microscopy (SEM) images. The presence of CPC micelles at a certain concentration may increase the effective concentration of the reactant in the hydrophobic part and resulting enhancement of the rate. The substrate undergoes effective collision with the expected positive reactive species Ce(SO4)2+ resulting enhancement of the rate. The enhanced local concentration of reactants in the interfacial region of CPC reverse micelle increases the observed rate. The Ru(III) catalyzed oxidation rate has been found to increase up to 5000 fold in micellar media compared to aqueous media. Ru(III) in combination with CPC is the most effective and suitable catalyst for the catalytic oxidation of p-chlorobenzaldehyde to p-chlorobenzoic acid.

Kinetics of micellar catalysis on oxidation of p-anisaldehyde to p-anisic acid in aqueous medium at room temperature

Oxidation of p-anisaldehyde by chromic acid produces p-anisic acid under kinetic condition [p-anisaldehyde]T≫[Cr(VI)]T. This oxidation reaction is performed also in presence of micellar catalysts in aqueous media at room temperature. The progress of the reaction is monitored spectrophotometrically by following the decay of Cr(VI) at 450nm wavelength. The product is confirmed by 1H NMR spectroscopy. Anionic surfactant sodium dodecyl sulfate (SDS) accelerated the reaction almost three-fold compared to uncatalyzed path, whereas cationic surfactant N-cetylpyridinium chloride (CPC) and neutral surfactant triton-X-100 (TX-100) inhibited the reaction.

Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on propanol to propionaldehyde conversion in aqueous media

Oxidation of propanol by chromic acid produces propionaldehyde under kinetic condition [propanol]T≫[Cr(VI)]T. This oxidation reaction is performed also in presence of micellar catalysts (anionic, cationic and neutral) and hetero-aromatic nitrogen bases promoters (picolinic acid, 2,2′-bipyridine, 1,10-phenanthroline) in aqueous media. The product is confirmed by 2,4-DNP test and 1H NMR spectroscopy. Anionic surfactant sodium dodecyl sulphate (SDS), neutral surfactant triton X-100 (TX-100) accelerated the reaction both in presence and absence of promoters whereas cationic surfactant N-cetyl pyridinium chloride (CPC) inhibited the reaction. Combination of SDS and bipy is found to be the most efficient for this oxidation.

Effect of Hofmeister anions on micellization and micellar growth of the surfactant cetylpyridinium chloride

Controlling the morphological characteristics of micellar solutions is important for surfactant performance and for achieving desired properties. In this work we study how monovalent anions of the lyotropic series affect micellization, micellar transitions, and micellar growth of the cationic surfactant N-cetyl pyridinium chloride (CPyCl), with the aim of achieving a tool to methodically tune these self-assembly characteristics. For the first time, a set of ions of the Hofmeister series were studied by combining indirect (surface tension, conductivity, optical absorption, viscosity, dynamic light scattering) and direct-imaging cryogenic-transmission electron microscopy (cryo-TEM). Following recent literature on anionic surfactants, we considered the pyridinium headgroup as a chaotropic cation, interacting with cosmotrope and chaotrope anions (Cl(-), Br(-), NO(3)(-), ClO(3)(-)). We show that the micelles' structure is strongly influenced by both the nature and concentration of added anions and their location in the lyotropic series, but the lyotropic number by itself cannot explain all the effects measured. Especially interesting was the relatively small effect of the chlorate ion on the CMC, but its large effect on micellar transition and growth. We further test the influence of a hydrotrope on the first and second CMC and micellar growth, and compare it with the data obtained with the inorganic salts.

Micellar catalysis of chromium(VI) oxidation of ethane-1,2-diol in the presence and absence of 2,2′-bipyridine in aqueous acid media

The kinetics and mechanism of the Cr(VI) oxidation of ethane-1,2-diol in the presence and absence of 2,2′-bipyridine (bipy) in aqueous acid media were studied under the conditions [ethane-1,2-diol]T ≫ [Cr(VI)]T. Under the kinetic conditions, monomeric Cr(VI) was found to be kinetically active in the absence of bipy, whereas in the bipy-catalyzed path the Cr(VI)-bipy complex was the active oxidant. In this path, the Cr(VI)-bipy complex undergoes nucleophilic attack by the substrate to form a ternary complex which subsequently undergoes redox decomposition (through 2e transfer) leading to hydroxyethanol and the Cr(IV)-bipy complex. The Cr(IV)-bipy complex then participates further in oxidation of organic substrate, ultimately converted into inert Cr(III)-bipy complex. The uncatalyzed path shows a second-order dependence on [H+], while the bipy-catalyzed path shows a first-order dependence on [H+]. Both the uncatalyzed and bipy-catalyzed paths show first-order dependence on [ethane-1,2-diol]T and on [Cr(VI)]T. The bipy-catalyzed path is first-order in [bipy]T. All these patterns remain unaltered in the presence of externally added surfactants. The effects of a cationic surfactant, N-cetylpyridinium chloride (CPC), and an anionic surfactant, sodium dodecyl sulfate (SDS), on both the uncatalyzed and bipy-catalyzed paths were studied. CPC inhibits both the uncatalyzed and bipy-catalyzed paths, whereas SDS catalyzes the reactions. The observed micellar effects are explained by considering a distribution pattern of the reactants between the micellar and aqueous phases.

Studies on Characterisation of Kinetically Active Cerium(IV) Species in Oxidation of α-Hydroxy Acids in Aqueous Micellar Sulfuric Acid Media

Kinetics of the oxidation of α-hydroxy acids [HA], namely malic acid, lactic acid and mandelic acid, by Ce(IV) in aqueous sulfuric acid media have been investigated both in the absence and presence of the cationic surfactant, N-cetylpyridinium chloride (CPC) and the anionic surfactant, sodium dodecyl sulfate (SDS). Under the conditions [HA]  [Ce(IV)], the reaction exhibits first-order kinetics both in [Ce(IV)] and [HA]. The rate retarding effect of HSO4- has been analysed and it has been noted that both Ce(SO4)2+ and Ce(SO4)2 are kinetically active but their relative contribution depends on the nature of the α-hydroxy acid and surfactant. The different rate constants in the presence and absence of surfactants have been determined with the corresponding activation parameters. SDS has been found to accelerate the rate process for all three α-hydroxy acids. CPC has been found to retard the oxidation of malic acid more than the other two α-hydroxy acids. In fact, for lactic acid, the rate is more or less insensitive to CPC. All these findings, including the micellar effects, have been interpreted in terms of the proposed reaction mechanism and partitioning behaviour of the different kinetically active species of Ce(IV) between the aqueous and pseudomicellar phases.

Oxidation of d-glucose in the presence of 2,2′-bipyridine by Cr VI in aqueous micellar media: a kinetic study

The kinetics of Cr VI oxidation of d-glucose to the corresponding lactone in the presence and absence of 2,2′-bipyridine (bipy) has been carried out under the conditions, [ d-glucose] T ≫ [Cr VI] T at different temperatures in aqueous micellar media. The monomeric Cr VI species has been found to be kinetically active in the absence of bipy whereas in the bipy-catalysed path, the Cr VI–bipy complex has been found to be the active oxidant. In the bipy-catalysed path, the Cr VI–bipy complex undergoes nucleophilic attack by the substrate to form a ternary complex. The ternary complex spontaneously experiences a redox decomposition (through two-electron transfer) in the rate-determining step leading to the product lactone and Cr IV–bipy complex. The Cr IV–bipy complex then takes part in faster steps in the further oxidation of d-glucose and is ultimately converted into a Cr III–bipy complex. In the uncatalysed path, the Cr VI-substrate ester experiences acid catalysed redox decomposition (two-electron transfer) in the rate-determining step. The uncatalysed path shows a second order dependence on [H +] and a first order dependence on each of the reactants [ d-glucose] T and [Cr VI] T. In contrast, the bipy-catalysed path shows a first order dependence on each of the reactants [H +], [ d-glucose] T and [Cr VI] T. The bipy-catalysed path is first order in [bipy] T. These observations remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant, N-cetylpyridinium chloride (CPC) and anionic surfactant, sodium dodecyl sulfate (SDS) on both the uncatalysed and bipy-catalysed path has been studied. CPC inhibits both the uncatalysed and bipy-catalysed path, while SDS catalyses these reactions. The observed micellar effects have been explained by considering hydrophobic and electrostatic interactions between the surfactants and reactants.

Micellar effect on the reaction of chromium(VI) oxidation of D‐fructose in the presence and absence of picolinic acid in aqueous media: a kinetic study

AbstractThe kinetics and mechanism of the Cr(VI) oxidation of D‐fructose in the presence and absence of picolinic acid (PA) in aqueous acid media were studied under the conditions [D‐fructose]T ≫[Cr(VI)]T at different temperatures. Under the kinetic conditions, the monomeric species of Cr(VI) was found to be kinetically active in the absence of PA whereas in the PA‐catalysed path, the Cr(VI)–PA complex was considered to be the active oxidant. In this path, the Cr(VI)–PA complex undergoes a nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition through glycol splitting leading to the lactone of C5‐aldonic acid along with formaldehyde and the Cr(IV)–PA complex. The primary product formaldehyde undergoes further oxidation (in part) to form formic acid. Then the Cr(IV)–PA complex participates further in the oxidation of D‐fructose and ultimately is converted into the inert Cr(III)–PA complex. In the uncatalysed path, the Cr(VI)–substrate ester experiences an acid‐catalysed redox decomposition (2e transfer) in the rate‐determining step giving rise to the products. The uncatalysed path shows a second‐order dependence on [H+] whereas the PA catalysed path shows a fractional order in [H+]. Both paths show a first‐order dependence on [D‐fructose]T and [Cr(VI)]T. The PA‐catalysed path is first order in [PA]T. All these patterns remain unaltered in the presence of externally added surfactants. The effects of a cationic surfactant, N‐cetylpyridinium chloride (CPC), and an anionic surfactant, sodium dodecyl sulfate (SDS), on both the uncatalysed and PA‐catalysed paths were studied. CPC inhibits both the uncatalysed and PA‐catalysed paths whereas SDS catalyses the reactions. The observed micellar effects are explained by considering a distribution pattern of the reactants between the micellar and aqueous phases. The applicability of different kinetic models, e.g. the pseudo‐phase ion‐exchange model, the Menger–Portnoy model and the Piszkiewicz cooperative model, was tested to explain the observed micellar effects. The effect of [surfactant]T on the activation parameters was explored to rationalize the micellar effect. Copyright © 2001 John Wiley & Sons, Ltd.

Flow-injection spectrophotometric determination of nicotinic acid in micellar medium of N-cetylpyridinium chloride

A simple flow-injection (FI) method with spectrophotometric detection at 440 nm is proposed for the determination of nicotinic acid, which is based on the formation of a polymethine dye at room temperature. In the FI system, nicotinic acid is hydrolyzed with 0.2 M cyanogen bromide at pH 5 (acetic-acetate buffer) in a non-micellar medium. The glutaconic aldehyde formed is injected into a stream containing 0.1 M aniline at pH 7, in a 0.1 M micellar medium of the cationic surfactant N-cetylpyridinium chloride (NCPC), to produce the polymethine. The performance of NCPC is compared with that of other surfactants: cetyltrimethylammonium bromide (CTAB, cationic), sodium dodecyl sulphate (anionic), and Triton X-100 (non-ionic). In the presence of NCPC and CTAB, the coupling reaction increases its sensitivity in ×3.3 and ×2.6 factors, respectively. This effect is explained by the higher concentration of glutaconic aldehyde and aniline on the micelle surface due to electrostatic attraction and hydrophobic association to the cationic surfactant. The dispersion coefficient of the FI system was D=2.4, and the sampling rate, 95 samples per hour. The limit of detection was 1.2×10 −6 M and the coefficient of variation 1.0 and 0.8% for 1×10 −5 and 1×10 −4 M nicotic acid, respectively. The optimized manifold was applied to the determination of commercial pharmaceuticals containing nicotinic acid, with recoveries in the 96.7–101% range.

The Influence of a Simple Electrolyte KCI on Surfactant - Dye Interactions in Water Solution

The influence of a simple electrolyte KCI on the interactions between the anionic dyes C. I. Acid Orange 7 (AO7) and the cationic surfactant N-cetylpyridinium chloride (CPCl) in water solutions was studied. To determine the equilibrium association constants, which enabled us to make the conclusions about the strength of interactions the Method of Continuous Variations was used. The light absorption of mixed dye and surfactant solutions in the visible absorption range at 25°C was measured. The concentration of the dye in the measured solutions was up to 6· 10−5 mol-1−1 and the concentration of the surfactant was up to 1.2· 10−4 mol· 1−1, which is below the critical micelle concentration of surfactant in pure water. The molal concentrations of KCl in the measured solutions were 0, 0.1, 0.5 and 1 mol/kg. It was found that the addition of KCI reduces the tendency of the dye AO7 and the surfactant CPC1 to associate.