Selective heteroaromatic nitrogen base promoted chromium(VI) oxidation of isomeric pentanols in aqueous micellar media at room temperature

Unlocking the Catalytic Potential of Anionic Micelles: Insights into the Ce(IV)-Directed Phenylalanine Oxidation Kinetics in Asymmetric Hydrophobic Environments

The oxidation kinetics of phenylalanine (Phe) by Ce(IV) have been examined in both the absence and presence of aqueous micellar media with asymmetric tails, specifically using sodium dodecyl sulfate (SDS) and sodium tetradecyl sulfate (STS) surfactants. The reaction progress was monitored by observing a decrease in absorbance using UV-vis spectroscopy. Interestingly, the kinetic profile revealed a consistent increase in the observed rate constant values as the concentration of the surfactant increased. The kinetic results have been analyzed by using numerous experimental studies, such as dynamic light scattering (DLS), zeta potential, 1H NMR analysis, FT-IR spectroscopy, conductometry, scanning electron microscopy (SEM), fluorometry, time-correlated single-photon counting (TCSPC), and transmission electron microscopy (TEM). Micellar aggregates maintain their spherical shape in the presence of the substrate, even at higher surfactant concentrations, as revealed by microstructural analysis. The substrate molecules are encapsulated to a greater extent in the inner micellar core of STS micelles on account of the more hydrophobic nature of STS surfactants. Therefore, in STS micellar media, fewer substrate molecules diffuse to the Stern layer compared to the SDS micellar medium, resulting in fewer molecules participating in the oxidative transformation reaction. As a result, the rate enhancement of oxidation kinetics is less pronounced in STS micelles than in SDS micelles. A plausible mechanism that aligns with the kinetic results has been highlighted, along with the interpretation of the Piszkiewicz model, to explain the observed catalytic effect of both micellar mediums.

Application of surfactants as anticorrosive materials: A comprehensive review

Corrosion is the degradation of a metal due to its reaction with the environment. One of the most efficient ways of securing metal surfaces from corrosion is the use of corrosion inhibitors. Their efficacy is connected to their chemical composition, their molecular structures, and their adsorption affinities on the metal surface. This review article focuses on the prospects of different types of monomeric and gemini surfactants, mixed surfactants systems, surfactants- additives mixed systems, inhibitors-surfactants (as additives) mixed systems, and ionic liquid based surfactants as promising corrosion-inhibiting formulations in the aqueous phase and the role of surfactants in developing protective coatings. The analysis starts with an accurate overview of the characteristics, types, and structure-property-performance relationship of anti-corrosion formulations of such inhibitors.

Aggregation of Surfactants: Catalytic Reinforcement in Oxidation of Unsaturated E-Crotonaldehyde

In this work, the kinetics of the micellar catalyzed oxidation of the unsaturated aliphatic aldehyde, E-crotonaldehyde in aqueous medium under pseudo 1st-order reaction condition was spectrophotometrically investigated at 25 °C. In the spectrophotometric measurement, the rate of the reaction was recorded by the decreasing intensity of the metallic oxidant, hexavalent chromium [Cr(VI)], in acidic aliquots at 450 nm with varying concentration of surfactants and/or heteroaromatic promoters. Spectral evidences have been produced in favour of the mechanistic approach and the product formation.

Micellar and Transition Metal Ion Catalysed Oxidation of Pentanol in Aqueous Medium

Micelles and 4d- or 5d-transition metal ions have been proved to be effective catalysts for the oxidation of 1-pentanol by Ce(IV) in aqueous medium under pseudo 1st order reaction conditions at 258C. Although cationic micelles show a speed retarding effect, anionic SDS micelles accelerate the reaction rate. The Ir(III) and Ru(III) catalysed reactions show shorter half-lives at micromolar concentration. Active Ce(IV) species are also identified and an explanation of the different catalytic activities of metal ions and micelles is presented. The accumulation of the substrate in the Stern-layer of the SDS micelles is detected. The reaction product is confirmed by melting point analysis, a 2,4-DNP test, and by IR and NMR studies.

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.

Promising Biocompatible, Biodegradable, and Inert Polymers for Purification of Wastewater by Simultaneous Removal of Carcinogenic Cr(VI) and Present Toxic Heavy Metal Cations: Reduction of Chromium(VI) by Poly(ethylene glycol) in Aqueous Perchlorate Solutions

A spectrophotometric technique has been applied for studying the reduction of chromium(VI) by poly(ethylene glycol) (PEG) as water-soluble and nontoxic synthetic polymer at a constant ionic strength of 4.0 mol dm^-3 in the absence and presence of the ruthenium(III) catalyst. In the absence of the catalyst, the reaction orders in [Cr(VI)] and [PEG] were found to be unity and fractional first orders, respectively. The oxidation process was found to be acid-catalyzed with fractional second order in [H⁺]. The addition of Ru(III) was found to catalyze the oxidation rates with observation of zero-order reaction in [CrO₄ ^2-] and fractional orders in both [PEG] and [Ru(III)], respectively. The PEG reduces the soluble toxic hexavalent Cr(VI) as a model pollutant to the insoluble nontoxic Cr(III) complex, which is known to be eco-friendly and more safer from the environmental points of view. The acid derivative of PEG was found to possess high affinity for the removal of poisonous heavy metal ions from contaminant matters by chelation. Formation of the 1:1 intermediate complex has been kinetically revealed. A consistent reaction mechanism of oxidation was postulated and discussed.

A highly selective fluorescent probe for Al3+ based on bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone with aggregation-induced emission enhancement and gel properties

An efficient fluorescent probe, bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone (1), has been prepared for the selective sensing of Al³⁺ over other common metal ions in water-containing media. The 1:1 stoichiometry of 1 and Al³⁺ was determined from Job's plot and Benesti-Hildebrand plot. The binding constant was observed as 1.6×10⁵M^-1, and the limit of detection was found to be 0.36μM, which was far below the drinking water restriction of Al³⁺ by EPA (the maximum allowable value is 7.4μM). In addition, the inherent AIEE features of 1 were observed upon addition of water to DMSO solution due to the restriction of the intramolecular motion, which makes the molecular conformations rigid and planar. Moreover, 1 could act as a novel gelator to form thermo-reversible supramolecular organogel with significant green emission in DMSO-H₂O (v/v, 9:1) solution.

Extraction of Natural Surfactant Saponin from Soapnut (Sapindus mukorossi) and its Utilization in the Remediation of Hexavalent Chromium from Contaminated Water

In this study optimization of extraction conditions for saponin from soapnut (Sapindus mukorossi) has been investigated. This investigation showed that a better extraction of saponin can be achieved with increasing the dielectric constant of solvent employed. The best yield was attained in a 50% v/v aqueous ethanol medium. Another objective of the present study is to assess the thermodynamics of the uptake-reduction of hexavalent chromium in contaminated water samples using saponin. Pyrene has been employed to determine the critical micellar concentration (CMC) (in the UV-vis method of determination) of saponin as a spectroscopic probe. Thus, the effectiveness of the bio-surfactant as a self-motivated adsorbent for hexavalent chromium is investigated. Several physico-chemical parameters like contact time, sorbate concentration, pH and temperature have been determined. The findings of the investigation invoked a very efficient uptake of 213.48 mg g−1 of hexavalent chromium from the contaminated water sample at a lower value of pH 2 and temperature 35°C. It is observed that the method followed a pseudo-first order kinetics, where the evaluated ΔG0 has supported the sorption as a feasible and spontaneous process. The HR-MS, FTIR, steady state Fluorescence spectroscopy, HR-TEM and UV-Vis spectroscopy have been employed for the current scientific studies.

Partitioning of reactive yellow 86 between aqueous and micellar media studied by differential absorption spectroscopy

The present study describes the partitioning of a reactive dye, reactive yellow 86, between aqueous and micellar media of a cationic surfactant (cetyltrimethyl ammonium bromide, CTAB), as well as an anionic surfactant (sodium dodecyl sulphate, SDS). In a systematic investigation, we have recorded the UV–vis absorption spectra of the dye as a function of surfactant’s concentration above and below the critical micelle concentration (CMC). Absorption spectra display a red shift in the case of CTAB and a hypochromic shift upon using SDS. The partition coefficient (Kx) was calculated using differential absorption data, and the value of free energy of partition (ΔGp) was calculated using this Kx value. The results revealed that the dye is solubilized in CTAB micelles to a greater extent than in SDS micelles.

Surface-active ionic liquids in catalysis: Impact of structure and concentration on the aerobic oxidation of octanol in water

We present design and synthesis of surface-active ionic liquids for the application in micellar catalysis. A series of 1-methyl-3-dodecylimidazolium based ionic liquids with variable core structures including dicationic and zwitterionic ones was synthesized and characterized. These surface-active ionic liquids where applied in the aerobic oxidation of aliphatic alcohols to carbonyl compounds. A strong dependence on the ionic liquid concentration and structure was identified, which is in accordance with the concepts of micellar catalysis. Optimum conditions for the oxidation of 1-octanol could be identified, and the use of surface-active ionic liquids strongly improved the reaction performance compared to pure water. Under optimized conditions, it was possible to isolate up to 75% of octanoic acid using only small amounts of surface-active ionic liquid in a 0.05mM solution in water without further ligands.