Chromium(VI) oxidants having quaternary ammonium ions: studies on synthetic applications and oxidation kinetics

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.

Chemoenzymatic Synthesis of the New 3-((2,3-Diacetoxypropanoyl)oxy)propane-1,2-diyl Diacetate Using Immobilized Lipase B from Candida antarctica and Pyridinium Chlorochromate as an Oxidizing Agent

To exploit the hydrolytic activity and high selectivity of immobilized lipase B from Candida antarctica on octyl agarose (CALB-OC) in the hydrolysis of triacetin and also to produce new value-added compounds from glycerol, this work describes a chemoenzymatic methodology for the synthesis of the new dimeric glycerol ester 3-((2,3-diacetoxypropanoyl)oxy)propane-1,2-diyl diacetate. According to this approach, triacetin was regioselectively hydrolyzed to 1,2-diacetin with CALB-OC. The diglyceride product was subsequently oxidized with pyridinium chlorochromate (PCC) and a dimeric ester was isolated as the only product. It was found that the medium acidity during the PCC treatment and a high 1,2-diacetin concentration favored the formation of the ester. The synthesized compounds were characterized using IR, MS, HR-MS, and NMR techniques. The obtained dimeric ester was evaluated at 100 ppm against seven bacterial strains and two Candida species to identify its antimicrobial activity. The compound has no inhibitory activity against the bacterial strains used but decreased C. albicans and C. parapsilosis growth by 49% and 68%, respectively. Hemolytic activity was evaluated, and the results obtained support the use of the dimeric ester to control C. albicans and C. parapsilosis growth in non-intravenous applications because the compound shows hemolytic activity.

Highly Efficient N-Heterocyclic Carbene/Ruthenium Catalytic Systems for the Acceptorless Dehydrogenation of Alcohols to Carboxylic Acids: Effects of Ancillary and Additional Ligands

The transition-metal-catalyzed alcohol dehydrogenation to carboxylic acids has been identified as an atom-economical and attractive process. Among various catalytic systems, Ru-based systems have been the most accessed and investigated ones. With our growing interest in the discovery of new Ru catalysts comprising N-heterocyclic carbene (NHC) ligands for the dehydrogenative reactions of alcohols, we designed and prepared five NHC/Ru complexes ([Ru]-1–[Ru]-5) bearing different ancillary NHC ligands. Moreover, the effects of ancillary and additional ligands on the alcohol dehydrogenation with KOH were thoroughly explored, followed by the screening of other parameters. Accordingly, a highly active catalytic system, which is composed of [Ru]-5 combined with an additional NHC precursor L5, was discovered, affording a variety of acid products in a highly efficient manner. Gratifyingly, an extremely low Ru loading (125 ppm) and the maximum TOF value until now (4800) were obtained.

Highly active bidentate N-heterocyclic carbene/ruthenium complexes performing dehydrogenative coupling of alcohols and hydroxides in open air

A highly active and robust bidentate NHC/Ru complex for the acceptorless dehydrogenative coupling of alcohols and hydroxides in open air.

A general and efficient Mn-catalyzed acceptorless dehydrogenative coupling of alcohols with hydroxides into carboxylates

A general and efficient Mn-catalyzed acceptorless dehydrogenative coupling of alcohols with hydroxides into carboxylates has been developed.

UV-Vis spectrophotometric studies of self-oxidation/dissociation of quaternary ammonium permanganates (QAP) - impact of solvent polarity

Self-oxidation/dissociation of some quaternary ammonium permanganates (QAPs), such as cetyltrimethylammonium permanganate (CTAP) and tetrabutylammonium permanganate (TBAP), have been studied spectrophotometrically in six different organic solvent media of different polarities wherein the compounds show good solubility and stability. The optical densities of the substrates at zero time (ODo) and first-order rate constants of dissociation (k1) have been determined from their successive scanning for 40min. At comparable experimental conditions, absorption capabilities of the substrates are compared from the ODo values in various organic media; the stability of the solutions is compared from the successive scan spectra in those media. The ODo values and the k1 values have been plotted against some solvent parameters to understand their effects on the absorbance and reactivity of the QAPs. These data are also subjected to multiple regression analysis to explain the influence of various solvent parameters on the ion-pairing properties of the substrates, thus elucidating their effects on the process of self-oxidation/dissociation of the substrates.

A green and sustainable phosphine-free NHC-ruthenium catalyst for selective oxidation of alcohols to carboxylic acids in water

An efficient novel protocol is applied for direct synthesis of carboxylic acids from primary alcohols through catalytic dehydrogenation. This reaction occurs in water as the solvent and as the oxygen-atom source and no toxic oxidizing agent is involved.

Kinetics and Mechanism of the Oxidation of Oxyacids of Phosphorus by Benzimidazolium Dichromate

Oxidation of some lower oxyacids of phosphorus by benzimidazolium dichromate results in the formation of the corresponding oxyacids containing phosphorus in a higher oxidation state, via an intermediate complex formation.

Palladium containing periodic mesoporous organosilica with imidazolium framework (Pd@PMO-IL): an efficient and recyclable catalyst for the aerobic oxidation of alcohols

The application of a novel palladium containing ionic liquid based periodic mesoporous organosilica (Pd@PMO-IL) catalyst in the aerobic oxidation of primary and secondary alcohols under molecular oxygen and air atmospheres is investigated. It was found that the catalyst is quite effective for the selective oxidation of several activated and non-activated alcoholic substrates. The catalyst system could be successfully recovered and reused several times without any significant decrease in activity and selectivity. Moreover, the hot filtration test, atomic absorption spectroscopy (AA) and kinetic study with and without selective catalyst poisons showed that the catalyst works in a heterogeneous pathway without any palladium leaching in reaction solution. Furthermore, nitrogen-sorption experiment and transmission electron microscopy (TEM) image proved the superior stability of high-ordered PMO-IL mesostructure during reaction process. TEM image also confirmed the presence of well-distributed Pd-nanoparticles in the uniform mesochannels of the material. These observations can be attributed to the ionic liquid nature of PMO-IL mesostructure which facilitates the reaction through production, chemical immobilization and stabilization of active palladium nanoparticles, as well as preventing Pd-agglomeration during overall process.

K2S2O8/MoO3: An Oxidation Reagent for benzylic alcohols and trimethylsilyl and tetrahydropyranyl ethers

The oxidation of benzylic alcohols and trimethylsilyl (TMS) and tetrahydropyranyl (THP) ethers to their corresponding carbonyl compounds with K2S2O8 is efficiently promoted by the presence of MoO3.