Kinetic study of oxidation of paracetamol by water-soluble colloidal MnO2 in the presence of an anionic surfactant

Unraveling the Catalytic Dynamics of Mixed Micellar Assemblies: A Molecular Approach to Green Organic Oxidative Transformation Reaction

The formation of mixed micelles represents a promising strategy to enhance organic reactions in aqueous media, offering a sustainable approach to reaction optimization. This study investigates the catalytic oxidation of cyclohexanol by chromium(VI) under acidic conditions at 27 °C with reaction kinetics monitored using UV-vis spectroscopy. Three readily available surfactants, cationic cetylpyridinium chloride (CPC), non-ionic Brij-35 (polyoxyethylene (23) lauryl ether), and anionic sodium dodecyl sulfate (SDS), were utilized to construct two mixed micellar systems: cationic/non-ionic (CPC: Brij-35) and anionic/non-ionic (SDS: Brij-35). Both mixed micellar systems exhibited significant catalytic activity, with the CPC: Brij-35 system, at an equimolar ratio, enhancing the reaction rate by an impressive 13.97-fold, compared to a 9.87-fold increase observed for the SDS: Brij-35 system. The superior catalytic efficiency of the CPC: Brij-35 assembly is attributed to enhanced micellization, improved solubilization of cyclohexanol, and strong electrostatic interactions between the positively charged CPC and the slightly negatively charged Brij-35, as evidenced by zeta-potential measurements. The kinetic behavior of the reaction was meticulously analyzed via UV-vis spectroscopy, while the micellization phenomena were corroborated through dynamic light scattering, zeta potential analysis, scanning electron microscopy, and 1H NMR spectroscopy. Additionally, the critical micelle concentrations (CMC) of the individual surfactants and their mixed systems were determined by using tensiometric measurements, providing a deeper understanding of the micellization process. The study reveals a plausible reaction mechanism emphasizing the critical role of the reaction zone within mixed micellar assemblies. These findings establish mixed micelles as powerful catalytic platforms, advancing green chemistry through an enhanced reaction efficiency and sustainable processes in aqueous media.

Potential application of Micellar nanoreactor for electron transfer reactions mediated by a variety of oxidants: A review

Surfactant, either natural or synthetic, forms a different type of aggregates among which 'Micelle' is truly an important dynamic surfactant aggregate, having a different region to interact with several organic, inorganic, and biomolecules; therefore the practical use of micelle is rapidly growing day-to-day. Surfactant-micelle, looks like a reactor of nano-dimension, govern a variety of reactions in aqueous media extensively. Oxidation is one of the vital reaction, take a part in the course of several organic transformations which are not very easy to execute in water media alone due to the solubility problem. Moreover, in order to achieve a quick transformation overcoming several difficulties the utility of micellar media became an excellent innovation, that's why nowadays, the surfactant and its aggregates are a focus of interest to the researcher of synthetic field and thus its practical applicability has been tremendously cultivated over the few decades. It is, therefore, useful to introduce some basic concepts regarding the aggregation of surfactants. Subsequently, we emphasize the importance of micellar media on the kinetics of oxidation reactions mediated by several metal ions with a special emphasis on their catalytic role.

A chemiluminescence reaction consisting of manganese(IV), sodium sulfite, and sulfur- and nitrogen-doped carbon quantum dots, and its application for the determination of oxytetracycline

Sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) were prepared by a solid-phase hydrothermal method from cysteine and citric acid and characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and FTIR spectroscopy. These QDs were exploited as enhancers to amplify the chemiluminescence (CL) of manganese(IV)-sodium sulfite reaction. S,N-CQDs exceptionally enhanced the CL intensity of this system, around 900-fold. This effect was attributed to the energy transfer from SO₂^*, produced by reaction of Mn(IV) with SO₃^2-, to S,N-CQDs. The maximum wavelength of CL emission was 480 nm, which confirmed that the final emitting species was S,N-CQDs. After optimization of reaction conditions, the analytical applicability of S,N-CQD-Mn(IV)-SO₃^2- CL system was studied. In the presence of oxytetracycline, the CL intensity was significantly diminished. A linear relationship was observed between CL signal and the logarithm of oxytetracycline concentration in the range of 0.075-3.0 μM with a detection limit of 25 nM. This CL assay for oxytetracycline was used for analysis of spiked milk and water samples. Graphical abstractSchematic representation of the amplified chemiluminescence (CL) reaction consisting of sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) Mn(IV) and Na2SO3. Sub-micromolar levels of oxytetracycline can be determined by using this system.