Oxidation Of Aromatic Aldehydes Research Articles

Mechanism of aroma enhancement methods in accelerating Congou black tea acidification subjected to room temperature storage

Acidification of aroma-enhanced black tea during storage was studied. UPLC-Q-TOF/MS (Ultra Performance Liquid Chromatography and Quadrupole-Time of Flight Mass Spectrometer) and HPLC (High-Performance Liquid Chromatography) analysis of non-volatile substances and organic acids revealed a decrease of soluble sugars and amino acids in aroma-enhanced black tea, while an increase in organic acids such as oxalic acid, malic acid and quinic acid. Further in vitro experiments indicated that the acidification of aroma-enhanced tea during storage can be attributed to decomposition of sugars and amino acids by heating, oxidation of aromatic aldehydes. Meanwhile, the amino acids, catechins, soluble sugars and flavonoids that constitute the taste of black tea are further reduced, changing the taste composition of tea infusion and further increasing its acidity. This study revealed the reasons for black tea acidification during aroma enhancement and storage and provided a theoretical basis for improving black tea quality.

Selective Oxidative Cleavage of the C-C Bond in α,β-Epoxy Ketone into Carbonyl Compounds.

This method afforded aromatic carbonyl compounds under TBHP via selective oxidative cleavage of the C–C bond in α,β-epoxy ketones. Aromatic acid came from the aroyl section, and aromatic aldehyde came from the other aromatic group. TBHP acted as a free radical initiator and oxidant. The reaction within the solvent went through a ring-opening addition, cleavage of the C–C bond in the ethylene oxide section, and oxidation, affording the target compounds in moderate to good yields. The HPLC yield of aromatic aldehyde was up to 91%. The HPLC yield of aromatic acid was up to 99%. The reaction under solvent-free conditions gave two kinds of aromatic acids coming from different moieties of α,β-epoxy ketone via the further oxidation of aromatic aldehyde. The substituent effect was discussed, and the reaction mechanism was proposed. This method allowed the reaction to occur in a simple system metal-free.

Room Temperature Synthesis of Mequinol by Using Ionic Liquids as Homogeneous Recyclable Catalysts

For the synthesis of Mequinol (4-methoxy phenol), two acidic ionic liquids based on imidazolium cation (BMSIL and IMSIL) synthesized and characterized by FT-IR, 1H NMR, and CHNS analyses. Tan, the Baeyer–Villiger oxidation of para-anisaldehyde was studied with these ionic liquids, as the catalysts. The results showed that the BMSIL with more Bronsted acidic functions had higher catalytic activity than IMSIL and even sulfuric acid at room temperature. Furthermore, the different reaction parameters were studied and maximum conversion (99%) and selectivity (95%) of Mequinol was observed by using 5% BMSIL as a catalyst, H2O2 (30% solution) as oxidant, Methanol as solvent at 3.5 h, and room temperature condition. Also, we investigated the effect of different substituents in the aromatic ring of benzaldehyde and various solvents on the catalytic activity of BMSIL ionic liquid as the best catalyst in the oxidation of aromatic aldehydes. The results show that the protic solvent and electron-donating substituents in the para position of benzaldehyde favor the phenol product.

Direct Conversion of Aromatic Aldehydes into Benzamides via Oxidation with Potassium Permanganate in Liquid Ammonia

Oxidation of aromatic aldehydes by KMnO4 in liquid ammonia gives amides directly. The reaction proceeds satisfactorily when the aldehydes are activated by electron-withdrawing substituents on the ring.

Oxidation of aromatic aldehydes with potassium bromate–bromide reagent and an acidic catalyst

We report herein an easy oxidation procedure for converting aromatic aldehydes to aromatic carboxylic acids by use of a combination of commercially and readily available potassium bromate with potassium bromide in the presence of hydrochloric acid catalyst.

NHC-Catalyzed Aerobic Oxidation of Aromatic Aldehydes to Aryl Esters

NHC-Catalyzed Aerobic Oxidation of Aromatic Aldehydes to Aryl Esters

ChemInform Abstract: Bromate Exchange Resin as an Oxidizing Agent in Organic Synthesis.

Abstract Bromate exchange resin has been prepared by a simple elution technique and used for the oxidation of aromatic aldehydes to the carboxylic acids. Oxidation is carried out under biphasic condition. Work up is simple. Resin immobilized bromate ions have been used for the first time as an oxidizing agent in organic synthesis.

Kinetics and Mechanism of Oxidation of Aromatic Aldehydes by Imidazolium Dichromate in Aqueous Acetic Acid Medium

The kinetics of oxidation of benzaldehyde (BA) and para‐substituted benzaldehydes by imidazolium dichromate (IDC) has been studied in aqueous acetic acid medium in the presence of perchloric acid. The reaction is first order each in [IDC], [Substrate] and [H+]. The reaction rates have been determined at different temperatures and the activation parameters calculated. Electron withdrawing substituents are found to increase the reaction and electron releasing substituents are found to retard the rate of the reaction and the rate data obey the Hammett relationship. The products of the oxidation are the corresponding acids. The rate decreases with the increase in the water content of the medium. A suitable mechanism is proposed.

Kinetics and Correlation Analysis of Reactivity in the Oxidation of Aromatic Aldehydes by Butyltriphenylphosphonium Dichromate

The oxidation of a number of para-, meta- and ortho-substituted benzaldehydes by butyltriphenylphosphonium dichromate (BTPPD), in dimethyl sulphoxide, leads to the formation of the corresponding benzoic acid. The reaction is first-order with respect to BTPPD. Michaelis-Menten type kinetics were observed with respect to the aldehyde. The formation constants of the aldehyde-BTPPD complexes and the rates of their decomposition were determined at different temperatures. The reactions are catalysed by hydrogen ions and the dependence is of the second order. The oxidation of [2H] benzaldehyde (PhCDO) exhibited the presence of a substantial kinetic isotope effect. The rates of oxidation of meta- and para-substituted benzaldehydes were correlated in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes were correlated with tetraparametric LDRS equation. The oxidation of para- and ortho-substituted benzaldehydes are more susceptible to the delocalization effect than is the oxidation of meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric hindrance by the ortho-substituents. The rates of oxidation of benzaldehyde were determined in nineteen organic solvents. An analysis of the solvent effect by multiparametric equations indicated the greater importance of the cation-solvating power of the solvents. Suitable mechanisms have been discussed.

Oxidation of Aromatic Aldehydes Using Oxone

An eco-friendly procedure for the oxidation of aldehydes to carboxylic acids in water or a water-ethanol mixture using Oxone as the oxidant is described. An easy isolation of the precipitated product upon cooling the reaction mixture helps avoid the use of extraction solvents in the product isolation procedure. The use of eco-friendly solvents, a non-toxic reagent, and the elimination of extraction solvents in the procedure demonstrate important green chemistry themes to the students. The optimized experimental procedure reported herein allows students to successfully carry out the experiment, isolate the product, and characterize the purified product through melting point determination and 1H NMR spectroscopy during a three-hour laboratory period.

The Role of Modification of Surfaces of Mercury and Gold Electrodes in Oxidation of Aromatic Aldehydes

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Oxidation of Aromatic Aldehydes with Tetrabutylammonium Fluoride: Competition with the Cannizzaro Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

One Facile Preparation of N‐Aroyl‐N′‐arylsulfonylhydrazines by Oxidation of Aromatic Aldehyde N‐Arylsulfonylhydrazones with Bis(trifluoroacetoxy)iodobenzene.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Oxidation of Aromatic Aldehydes with Tetrabutylammonium Fluoride:Competition with the Cannizzaro Reaction

During the synthesis of 4-fluorobenzaldehyde via the SNAr reaction of 4-nitrobenzaldehyde with TBAF, it was found that an equivalent amount of TBAF could oxidize benzaldehyde to benzoic acid. The reaction of 4-nitrobenzaldehyde with tetrabutylammonium fluoride (TBAF) gave 4-nitrobenzoic acid in high yield. Depending on the reaction conditions, other aromatic aldehydes produced acids with fewer amounts of alcohols. However, this type of oxidation has limited practical applications. Nevertheless, the mechanism is quite different from the Cannizzaro reaction because the amounts of the acid salt and alcohol formed were different.

One Facile Preparation of N‐Aroyl‐N′‐arylsulfonylhydrazines by Oxidation of Aromatic Aldehyde N‐Arylsulfonylhydrazones with bis(Trifluoroacetoxy)iodobenzene

N‐aroyl‐N′‐arylsulfonylhydrazines can be obtained by oxidation of aromatic aldehyde N‐arylsulfonylhydrazones with bis(trifluoroacetoxy)iodobenzene in acetone at room temperature in mild to good yields.

Heterogeneous Method for the Oxidation of Alcohols under Mild Conditions with Zinc Dichromate Adsorbed on Alumina

Chromate salts and other chromium (VI) oxides have been widely used as oxidizing agents for a variety of substrates including alcohols. These oxidants are frequently used in large excess but can also be used catalytically in conjunction with secondary oxidants. Problems in the use of chromium (VI) complexes as oxidation reagents include the lack of selectivity in oxidations, safety hazards associated with the use of large quantities of toxic compounds, cumbersome preparation and potential danger (ignition) in handling its complexes, difficulties in terms of product isolation and waste disposal and the need for aqueous acidic or basic conditions for reactions of chromate salts. These problems could be eliminated by reagents on solid supports. Many oxidants, especially the older and stronger chromium oxidizing agents, may have their reactivity and selectivity modified by adsorption onto inert supports. There were many chromium oxidants on inert inorganic supports such as: pyridinium chlorochromate on alumina, pyridinium chromate on silica, chromic acid on alumina and silica, chromyl chloride on silica – alumina and resin, poly(vinyl pyridinium chlorochromate (PVPCC) and poly(vinyl pyridinium dichromate, chromium VI oxide prepared and used for the oxidation of organic compounds. In this paper, we wish to report the utilization of zinc dichromate onto alumina as a convenient, efficient and economical reagent for the oxidation of alcohol to carbonyl compounds in CH3CN, H2O and solvent–Free conditions. (Table 1, Scheme 1) The rate of oxidation and yield of product depended on the nature of the substrate and reaction condition. Oxidation of benzylic alcohols proceeded more rapidly than the oxidation of aliphatic alcohols (Table 1). In the oxidation of benzyl alcohols to benzaldehyde, when there is an electron releasing group, the rate and yield of the reaction increased (Entry 1-3). 4-Nitro benzyl alcohol is oxidized to its corresponding aldehyde within a longer time and 80-85% yield. Primary and secondary aliphatic alcohols (Entry 1012) are oxidized to the corresponding carbonyl compounds under these conditions. Reaction in solvent–Free conditions is of a high yield and faster than reactions in water and acetonitrile. The reactions are relatively clean with no tar formation and no over oxidation to carboxylic acids. The reaction of cinnamyl alcohol gave cinnamaldehyde with a high yield without cleavage of benzylic double bond. (Entry 9) The acidity of zinc dichromate/Alumina (pH of 0.01 molar solution: 4.65) is less pronounced than those reported for pyridinium chlorochromate (pH of a 0.01 molar solution: 1.75) and pyridinium fluorochromate (pH of a 0.01 molar solution: 2.45). This reaction has several interesting features: 1) Yields are satisfactory. 2) The reaction is specific, avoiding over oxidation of aromatic aldehyde into acid. 3) The reagent is cheap and easy to prepare. 4) The reaction is performed under mild conditions, in CH3CN, H2O and solvent-free at room temperature. 5) The experimental set-up and work-up are exceedingly simple.

In Situ Generation of Carboxylate: An Efficient Strategy for a One-Pot Synthesis of Homo- and Heterometallic Polynuclear Complexes

An efficient strategy for synthesis of a wide range of homo- and heterometallic polynuclear complexes is proposed. The synthesis protocol consists of a two-step one-pot reaction. The first step is the in situ generation of carboxylate anions via oxidation of aromatic aldehydes by metal nitrates in air. The aldehydes act as solvents and are also involved in redox processes. Solutions containing solely transition metal cations and aromatic carboxylates are obtained following this procedure. The second step is a tunable "à la carte" formation of a series of various polynuclear carboxylato complexes from solutions obtained at the former stage upon addition of different solvents. The polarity and donor properties of the solvents play a key role in determination of the nuclearities of the complexes. Hydrolytic processes can induce the formation of oxo- or hydroxo-bridges inside the polynuclear core as well. Complexes of various nuclearities are obtained: from discrete tri-, hexa-, or octanuclear units to 1D polymers. This protocol can be adapted with disconcerting simplicity to the synthesis of heterometallic species with similar molecular structures to their homometallic analogues starting from stoichiometric mixture of metal nitrates under the same reaction conditions. Detailed description of synthesis and the molecular structure of one representative complex for each series are presented in this paper. The temperature dependence of magnetic susceptibility of the heterometallic 1-D MnCo chain reveals typical behavior of a ferrimagnetic chain. The low-temperature investigations on single crystals show significant Ising type magnetic anisotropy.

Oxidation of Aromatic Aldehydes and Ketones by H2O2/CH3ReO3 in Ionic Liquids: A Catalytic Efficient Reaction to Achieve Dihydric Phenols.

Abstract A convenient and efficient application of hydrogen peroxide/methyltrioxorhenium in ionic liquids [bmim]BF4 and [bmim]PF6 for the oxidation of hydroxylated and methoxylated benzaldehydes and acetophenones to the corresponding phenols is described. Good yields of products were obtained in short reaction times.

Oxidation of aromatic aldehydes and ketones by H 2O 2/CH 3ReO 3 in ionic liquids: a catalytic efficient reaction to achieve dihydric phenols

A convenient and efficient application of hydrogen peroxide/methyltrioxorhenium in ionic liquids [bmim]BF 4 and [bmim]PF 6 for the oxidation of hydroxylated and methoxylated benzaldehydes and acetophenones to the corresponding phenols is described. Good yields of products were obtained in short reaction times.

ChemInform Abstract: The Oxidation of Aromatic Aldehydes by Magnesium Monoperoxyphthalate and Urea—Hydrogen Peroxide.

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