Method For Oxidation Of Alcohols Research Articles

Continuous-flow synthesis of carboxylic acids from alcohols via platinum and silicon dioxide-catalyzed hydrogen peroxide oxidation.

A continuous-flow method for the direct oxidation of alcohols to carboxylic acids is reported, employing hydrogen peroxide (H2O2) and a platinum (Pt) catalyst within a flow reactor system. This approach allows for precise control over the contact time between the reactants and the catalyst, enabling optimization of reaction conditions. By analyzing the yields of both aldehydes and carboxylic acids as a function of weight hourly space velocity (WHSV), selective synthesis of carboxylic acids was achieved without the formation of corresponding aldehydes. The Pt catalyst exhibited excellent stability, producing 25.2 g of octanoic acid from 1-octanol with a yield exceeding 96% over 210 h at a WHSV of 1.3 h-1 using a 5 mm inner diameter × 100 mm column. This Pt-catalyzed continuous-flow H2O2 oxidation method demonstrates good reactivity for a variety of alcohols, including aliphatic, aromatic, allylic, and heteroaromatic, affording the corresponding carboxylic acids in 19-98% isolated yields with water as the sole byproduct. X-ray photoelectron spectroscopy (XPS) analysis confirmed the preservation of metallic zero-valent Pt (Pt(0)) throughout the reaction.

Copper on charcoal: TEMPO free Cu0 nanoparticles catalyzed aerobic oxidation of alcohols

A highly efficient and Tempo-free catalytic aerobic alcohol oxidation method has been developed using charcoal-supported Cu0 nanoparticles（Cu-A） in conjunction with pyridine. Various alcohols, bearing different functional groups, can be readily oxidized to their corresponding ketones and aldehydes under mild conditions.

Electrocatalytic alcohol oxidation by a molecular iron complex.

An efficient electrochemical method for the selective oxidation of alcohols to their corresponding aldehydes/ketones using a biomimetic iron complex, [(bTAML)FeIII-OH2]-, as the redox mediator in an undivided electrochemical cell with inexpensive carbon and nickel electrodes using water as an oxygen source is reported. The substrate scope also includes alcohols that contain O and N heteroatoms in the scaffold, which are well tolerated under these reaction conditions. Mechanistic studies show the involvement of a high-valent FeV(O) species, [(bTAML)FeV(O)]-, formed via PCET (overall 2H+/2e-) from [(bTAML)FeIII-OH2]- at 0.77 V (vs. Fc+/Fc). Moreover, electrokinetic studies of the oxidation of C-H bonds indicate a second-order reaction, with the C-H abstraction by FeV(O) being the rate-determining step. The overall mechanism, studied using linear free energy relationships and radical clocks, indicates a "net hydride" transfer, leading to the oxidation of the alcohol to the corresponding aldehyde or ketone. When the reaction was carried out at pH > 11, the reaction could be carried out at a ∼500 mV lower potential than that at pH 8, albeit with reduced reaction rates. The reactive intermediate involved at pH > 11 is the corresponding one-electron oxidized [(bTAML)FeIV(O)]2- species.

ÁLCOOL EM GEL PARA ASSEPSIA DAS MÃOS – FORMULAÇÃO ADEQUADA E EFICIÊNCIA GARANTIDA EM MEIO À PANDEMIA DA COVID-19

ALCOHOL GEL FOR ASEPSY OF THE HANDS – PROPER FORMULATION AND GUARANTEED EFFICIENCY AMID THE PANDEMIC OF COVID-19. The use of hand antiseptics became widespread as a routine in the fight against COVID-19. In the market, the availability and purchase of substandard antiseptics create a permanent concern with safety, even after a pandemic. Therefore, the development of easy-to-deploy analytical methods for the quality control of alcohol-based hand antiseptics is needed. In this work, to determine the ethanol content in alcohol gel the use of refractometry and alcohol oxidation method by dichromate accompanied by UV-Vis spectroscopy were applied. The results indicated that 19 brands (out of the 70 evaluated) (27.1%) had levels of ethyl alcohol below the recommended level (68.25%), therefore, they are ineffective for hand asepsis. For the quality control of hand antiseptics, refractometry and the oxidation-reduction reaction are complementary analytical methodologies. As a quick, inexpensive screening method, refractometry provides a more suitable technique. However, the interference of emollients may affect the accuracy of the ethanol content determination. Therefore, applying the ethanol oxidation method coupled with electronic spectroscopy offers a simple and broadly accessible method to confirm the ethanol content in alcohol-based hand antiseptics. In addition to developing quality control protocols, is also described the 3.5-ton production of alcohol gel at the Federal University of Bahia.

Sequential Connection of Mutually Exclusive Catalytic Reactions by a Method Controlling the Presence of an MOF Catalyst: One-Pot Oxidation of Alcohols to Carboxylic Acids.

A functionalized metal-organic framework (MOF) catalyst applied to the sequential one-pot oxidation of alcohols to carboxylic acids controls the presence of a heterogeneous catalyst. The conversion of alcohols to aldehydes was acquired through aerobic oxidation using a well-known amino-oxy radical-functionalized MOF. In the same flask, a simple filtration of the radical MOF with mild heating of the solution completely altered the reaction media, providing radical scavenger-free conditions suitable for the autoxidation of the aldehydes formed in the first step to carboxylic acids. The mutually exclusive radical-catalyzed aerobic oxidation (the first step with MOF) and radical-inhibited autoxidation (the second step without MOF) are sequentially achieved in a one-pot manner. Overall, we demonstrate a powerful and efficient method for the sequential oxidation of alcohols to carboxylic acids by employing a readily functionalizable heterogeneous MOF. In addition, our MOF in-and-out method can be utilized in an environmentally friendly way for the oxidation of alcohols to carboxylic acids of industrial and economic value with broad functional group tolerance, including 2,5-furandicarboxylic acid and 1,4-benzenedicarboxylic acid, with good yield and reusability. Furthermore, MOF-TEMPO, as an antioxidative stabilizer, prevents the undesired oxidation of aldehydes, and the perfect "recoverability" of such a reactive MOF requires a re-evaluation of the advantages of MOFs from heterogeneity in catalytic and related applications.

Hydrotalcite-Supported Ag/Pd Bimetallic Nanoclusters Catalyzed Oxidation and One-Pot Aldol Reaction in Water

A highly active hydrotalcite-supported Ag/Pd bimetallic nanocluster catalyst has been developed by a simple, easy and safe chemical reduction method. The catalyst was characterized by high-resolution transmission electron microscopy (HR-TEM), which revealed very small (3.2 ± 0.7 nm) nanoclusters with a narrow size distribution. The bimetallic Ag/Pd catalyst showed strong cooperation between Ag and Pd for the alcohol oxidation reaction. The developed catalyst provided an efficient and environmentally friendly method for alcohol oxidation and one-pot cross-aldol condensation in water. A broad scope of α,β-unsaturated ketones with good to excellent yields were obtained under very mild conditions. This catalytic system offers an easy preparation method with a simple recovery process, good activity and reusability of up to five cycles without significant loss in the catalytic activity.

Electrochemical Oxidation of Organic Molecules at Lower Overpotential: Accessing Broader Functional Group Compatibility with Electron-Proton Transfer Mediators.

Electrochemical organic oxidation reactions are highly appealing because protons are often effective terminal electron acceptors, thereby avoiding undesirable stoichiometric oxidants. These reactions are often plagued by high overpotentials, however, that greatly limit their utility. Single-electron transfer (SET) from organic molecules generates high-energy radical-cations. Formation of such intermediates often requires electrode potentials far above the thermodynamic potentials of the reaction and frequently causes decomposition and/or side reactions of ancillary functional groups. In this Account, we show how electrocatalytic electron-proton transfer mediators (EPTMs) address this challenge. EPTMs bypass the formation of radical-cation intermediates by supporting mechanisms that operate at electrode potentials much lower (≥1 V) than those of analogous direct electrolysis reactions.The stable aminoxyl radical TEMPO (2,2,6,6-tetramethylpiperidine N-oxyl) is an effective mediator for electrochemical alcohol oxidation, and we have employed such processes for applications ranging from pharmaceutical synthesis to biomass conversion. A complementary electrochemical alcohol oxidation method employs a cooperative Cu/TEMPO mediator system that operates at 0.5 V lower electrode potential than the TEMPO-only mediated process. This difference, which arises from a different catalytic mechanism, rationalizes the broad functional group tolerance of Cu/TEMPO-based aerobic alcohol oxidation catalysts.Aminoxyl mediators address long-standing challenges in the "Shono oxidation," an important method for α-C-H oxidation of tertiary amides and carbamates. Shono oxidations are initiated by a high-potential SET step that limits their utility. Aminoxyl-mediated Shono-type oxidations have been developed that operate at much lower potentials and tolerate diverse functional groups. Analogous reactivity underlies α-C-H cyanation of secondary cyclic amines, a new method that enables efficient diversification of piperidine-based pharmaceutical building blocks and preparation of non-natural amino acids.Electrochemical oxidations of benzylic C-H bonds are commonly initiated by SET to generate arene radical cations, but such methods are again plagued by large overpotentials. Mediated electrolysis methods that promote hydrogen-atom-transfer (HAT) from benzylic C-H bonds to Fe-oxo species and phthalimide N-oxyl (PINO) support C-H oxygenation, iodination, and oxidative-coupling reactions. A complementary method merges photochemistry with electrochemistry to achieve amidation of C(sp3)-H bonds. This unique process operates at much lower overpotentials compatible with diverse functional groups.These results have broad implications for organic electrochemistry, highlighting the importance of "overpotential" considerations and the prospects for expanding synthetic utility by using mediators to bypass high-energy outer-sphere electron-transfer mechanisms. Principles demonstrated here for oxidation are equally relevant to electrochemical reductions.

Aerobic oxidation of alcohols using bismuth bromide as a catalyst

We developed an environmentally friendly method for aerobic oxidation of alcohols using a commercially available, relatively benign bismuth salt as a catalyst. We found that the catalytic combination of BiBr3 with nitric acid is key for enhancing the reactivity. The reaction proceeds well under air, making the use of pure oxygen unnecessary. Each of the primary or secondary alcohols tested was oxidized to the corresponding aldehydes or ketones using this protocol.

A Novel MPTHP Modified Glassy Carbon Sensor Electrode: Investigation of Electrochemical Behaviors and Determination of Cu (II) Ions in Drinking Water Sample

In the present work report, 2-methyl-6-((2-(4-(3-methyl-3-phenylcyclobutyl)thiazol-2-yl)hydrazono)methyl) phenol (MPTHP) has been newly synthesized and characterized. The new molecule has been used to modify the glassy carbon (GC) electrode surface through the alcohol oxidation method due to –OH group on its structure. MPTHP modified GC (MPTHP/GC) electrode has been used as a chemical sensor electrode for the quantitative determination of Cu (II) ions. Following the modification process, the surface characterization process of the modified electrode has been carried out by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). In this work, Cu (II) ions have been quantitatively determined by using differential pulse voltammetry (DPV) technique. A quite low detection limit (based on 3sbl/m) for Cu (II) using developed sensor electrode was found to be as 1.0x10-9 M. For the calibration curve, solutions of Cu (II) ions changing from 1.0x10-9 M to 1.0x10-3 M have been prepared using Britton-Robinson (BR) buffer solution at pH 5. The developed sensor electrode has been applied to tap water sample for the quantitation of Cu (II) ions and the amount of Cu (II) was determined as 4.07 x 10-9 M in this sample.

AgCu/SiC-powder: A highly stable and active catalyst for gas-phase selective oxidation of alcohols

Highly active and selective bimetallic AgCu/SiC-powder catalysts have been prepared by a facile method for the gas-phase selective oxidation of alcohols (such as 99.3% benzyl alcohol conversion and 99.6% benzyl aldehyde selectivity). The catalytic activity can maintain at least 200h compared with Cu/SiC (only within 10h). The formation of Ag-Cu2O ensembles brings about enhanced improvement both in conversion and stability. The XPS results reveal that large amounts of Ag0-Cu2O active sites formed after pre-activation process and Cu2O sites play a dominant role in benzyl alcohol oxidation reaction. Dehydrogenation reaction process has also been confirmed by O2-TPD.

Preparation of Au nanoparticles with high dispersion and thermal stability by a controlled impregnation method for alcohol oxidation

Gold nanoparticles are attractive in catalytic field due to their high activity and selectivity. However, dispersion and sintering resistance have been two of the biggest issues in catalysis for preparation of gold nanoparticles. In this paper, a controlled impregnation method was employed to prepare highly dispersed and thermally stable Au-based catalysts for aerobic oxidation of benzyl alcohol. The size of hydrotalcites (HTs)-supported Au nanoparticles was 2.8 nm at 300 °C of calcination temperature, which was 3.2 nm when calcination temperature was increased to 600 °C. The mechanism of forming metal nanoparticles was proposed. The high dispersion of Au was ascribed to the directing role of Cu and the interaction between Au (and Pt) and Cu. It was proposed that the thermal stability of Au nanoparticles was due to the simultaneous employment of multiple additional effects. The activity of Au nanoparticles was far higher than those prepared by traditional methods. Furthermore, the PtCu elements in Au nanoparticles were homogeneously distributed. In contrast, they were randomly distributed in Au nanoparticles prepared by the traditional method.

Manganese (III) salophen supported on nanosilica triazine dendrimer as a selective heterogeneous catalyst for oxidation of alcohols with sodium periodate

In this paper, we present an efficient and practical method for oxidation of alcohols to their corresponding carbonyl compounds catalyzed by [Mn(salophen)@nSTD]. This catalyst was synthesized, and characterized by FT-IR, UV–Vis, TGA, SEM and TEM. The results of experiments proved that this catalyst has excellent selectivity and high activity in the oxidation of different primary and secondary alcohols to their corresponding aldehyde and ketone at room temperature. The effects of important factors in the oxidation of alcohols such as kind of oxidant, solvent and amount of catalyst were investigated in the oxidation of 4-chlorobenzyl alcohol. This catalyst shows high stability and reusability after six catalytic runs.

Correction: Novel approach to synthesizing polymer-functionalized Fe3O4/SiO2–NH2via an ultrasound-assisted method for catalytic selective oxidation of alcohols to aldehydes and ketones in a DMSO/water mixture

Correction for ‘Novel approach to synthesizing polymer-functionalized Fe3O4/SiO2–NH2via an ultrasound-assisted method for catalytic selective oxidation of alcohols to aldehydes and ketones in a DMSO/water mixture’ by Mahsa Dehghan et al., RSC Adv., 2015, 5, 92335–92343.

Iodine catalyzed oxidation of alcohols and aldehydes to carboxylic acids in water: a metal-free route to the synthesis of furandicarboxylic acid and terephthalic acid

Iodine(iii) catalyzed metal free method for oxidation of alcohols and aldehydes in water.

Preparation of PtRu/C core–shell catalyst with polyol method for alcohol oxidation

Carbon supported PtRu core–shell catalyst is prepared by a facile and efficient method, in which the Ru nanoparticles are prepared with microwave-assisted method followed by in-situ reduction of Pt on Ru nanoparticles forming the PtRu core–shell structure. The catalyst is characterized by energy-dispersive X-ray spectroscope (EDX) analyzer attached to scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The TEM results show that the synthesized PtRu/C catalysts have small particle size and narrow size distribution. The PtRu/C catalyst shows higher electrochemical performance toward ethanol oxidation reaction (EOR) compared with methanol oxidation reaction (MOR). Notably, the PtRu/C catalysts exhibit higher mass activity and stability than that of the commercial PtRu/C (JM) catalyst for ethanol electrooxidation.

Hydroformylation: Fundamentals, Processes, and Applications in Organic Synthesis

Highly active and selective bimetallic AgCu/SiC-powder catalysts have been prepared by a facile method for the gas-phase selective oxidation of alcohols (such as 99.3% benzyl alcohol conversion and 99.6% benzyl aldehyde selectivity). The catalytic activity can maintain at least 200 h compared with Cu/SiC (only within 10 h). The formation of Ag-Cu2O ensembles brings about enhanced improvement both in conversion and stability. The XPS results reveal that large amounts of Ag0-Cu2O active sites formed after pre-activation process and Cu2O sites play a dominant role in benzyl alcohol oxidation reaction. Dehydrogenation reaction process has also been confirmed by O2-TPD.

Development of a Metal-Free Oxidation of Alcohols with Dimethyl Sulfoxide (DMSO) Activated by Tosyl Chloride

In this article we propose an efficient metal-free method for the mild oxidation of alcohols using dimethyl sulfoxide/tosyl chloride at ambient temperature. The procedure described here is an easy and practical method for the oxidation of primary, secondary, allylic, and benzylic alcohols into their corresponding aldehydes and ketones. The notable advantages of this protocol are mild reaction conditions, good yields and selectivity, and simple workup with minimal waste containing no metallic components. The mechanism of the transformation is also investigated.

ChemInform Abstract: A Mild and Highly Efficient Laccase‐Mediator System for Aerobic Oxidation of Alcohols

Abstract25 examples

ChemInform Abstract: Anaerobic Nitroxide‐Catalyzed Oxidation of Alcohols Using the NO+/NO· Redox Pair.

A new method for alcohol oxidation using TEMPO or AZADO in conjunction with BF3·OEt2 or LiBF4 as precatalysts and tert-butyl nitrite as a stoichiometric oxidant has been developed. The system is based on a NO+/NO· pair for nitroxide reoxidation under anaerobic conditions. This allows the simple, high-yielding conversion of various achiral and chiral alcohols to carbonyl compounds without epimerization and no formation of nonvolatile byproducts.

Anaerobic Nitroxide-Catalyzed Oxidation of Alcohols Using the NO+/NO· Redox Pair

A new method for alcohol oxidation using TEMPO or AZADO in conjunction with BF3·OEt2 or LiBF4 as precatalysts and tert-butyl nitrite as a stoichiometric oxidant has been developed. The system is based on a NO(+)/NO· pair for nitroxide reoxidation under anaerobic conditions. This allows the simple, high-yielding conversion of various achiral and chiral alcohols to carbonyl compounds without epimerization and no formation of nonvolatile byproducts.