Ozone In Acetic Acid Research Articles

Insights into product selectivity of alkylbenzenes oxidation by ozone in acetic acid

The selectivity of the oxidation of alkylbenzenes under ozone in acetic acid has been investigated. The use of the catalytic system Co(II) acetate - CH3COOH - CHal3COOH exhibited its high efficiency in the production of aromatic acids (benzoic and phtalic acids) and toluene as the main reaction products, with minor production of ketones (benzophenone) under specific reaction conditions. In the process, Co (II) transforms into Co (III). Co (III) initiates the selective oxidation of alkylbenzenes while being reduced to Co (II). In the presence of ozone, this process is continues with time. The kinetic parameters of the main stages of the catalytic cycle were determined.

Catalytic oxidation of 4-nitroethylbenzen by ozone in acetic acid

Catalytic oxidation of 4-nitroethylbenzen by ozone in acetic acid

The oxidation of 4-bromacetophenone by ozone in acetic acid

The kinetics and mechanism of oxidation of 4-bromoacetophenone by ozone in acetic acid solution have been studied. It was shown that 77% of the starting material is oxidized by the benzene ring; 8% of 4-bromobenzoic acid and small amounts of carbon (IV) oxide were identified among the side chain ozonation products. The main reaction products are aliphatic peroxide compounds, which have in their structure one hydroperoxide group. Manganese (II) acetate was shown to be the most effective catalyst for the side chain reaction of 4-bromoacetophenone in acetic acid. High selectivity for the side chain is achieved only at sufficiently high concentrations of catalyst ([Mn(OAc)2]0:[ArH]0=1:4). The main product of the catalytic oxidation of 4-bromoacetophenone is 4-bromobenzoic acid with a yield of 82.5%. The found dependences of the rate of oxidation of 4-bromoacetophenone by ozone on the concentration of reactants are described by the kinetic equation of the third order, the reaction rate has the first order with respect to each reagent. It was found that the decisive role in the selective oxidation of 4-bromoacetophenone is played by two-stage oxidation, in which ozone predominantly reacts with the reduced form of manganese, and the introduction of the substrate into side chain oxidation is carried out by the reaction with the oxidized form of metal. According to the research results, the mechanism of catalytic ozonation of 4-bromoacetophenone in acetic acid has been proposed, which involves ion-radical non-chain oxidation of the substrate.

Investigation of catalytic oxidation of 4-nitroethylbenzene by ozone to 4-nitroacetophenone – an intermediate in the synthesis of antibiotics

4-Nitroacetophenone is an important intermediate for the manufacture of broad-spectrum antibiotics, in particular chloramphenicol. Existing methods of ketone synthesis are imperfect. The disadvantage of the simplest of them (the oxidation of 4-nitroethylbenzene by oxygen at atmospheric pressure and temperature of 135 °C, in the presence of manganese oxide) is the low yield and the need for the process in a heterogeneous environment. Therefore, the development of affordable and inexpensive ways to obtain 4-nitroacetophenone is an actual task. The aim of the work is to investigate the products and kinetics of the reaction of catalytic oxidation of 4-nitroethylbenzene by ozone in acetic acid and to develop a new low-temperature synthesis of 4-nitroacetophenone. Materials and methods. The experiments were used 4-nitroethylbenzene, 4-nitroacetophenone and 1-(4-nitrophenyl)ethanol by company Acros organics qualification “puriss.”; manganese (II) acetate qualification “puriss.”; as a solvent – glacial acetic acid by company Sigma qualification “puriss.”. A spectrophotometric method was used to continuously monitor the current concentration of ozone in the gas phase. A Teflon flow cell with quartz windows was installed in the measuring chamber of the SF-46 LOMO spectrophotometer, which allowed the measurement of the optical density of the gas flow in the UV region. The concentration of ozone at the inlet and outlet of the reactor was determined by recording the results on the potentiometer KSP-4 in the form of an ozonogram when passing ozone-containing gas through a cuvette at a wavelength of a monochromatic light source 254–256 nm. The quantitative content of the reaction mixture was performed using gas-liquid chromatography, calculations of the concentration of components were performed by the method of internal standard. Results. The products and kinetics of the reaction of ozone with 4-nitro-ethylbenzene in the presence of a catalyst – manganese (II) acetate were studied. It was found that at a temperature of 20 °C the oxidation process proceeds mainly along the side chain, while the yield of 4-nitroacetophenone reaches 98.5 %, also the system identified trace amounts of 1-(4-nitrophenyl)ethanol. This fact is explained by the fact that ozone under catalysis conditions preferably reacts not with the substrate, but with Mn (II) with the formation of the active form of Mn (IV) which, in turn, is reduced by reaction with 4-nitroethylbenzene, and thus initiates oxidation of the substrate. on the side chain. Conclusions. Catalytic oxidation of 4-nitroethylbenzene by ozone in acetic acid solution proceeds mainly along the side chain to form 4-nitroacetophenone with a yield of 98.5 %. The optimum reaction temperature is 20–30 °C, as its increase deepens the oxidation process and the ketone begins to be converted into 4-nitrobenzoic acid.

Liquid-phase oxidation of 2-chlorotoluene with ozone to 2-chlorobenzoic acid – an intermediate for diclofenac sodium production

2-Chlorobenzoic acid is used as an intermediate for diclofenac sodium production. In industry, it is obtained by oxidation of 2-chlorotoluene with potassium permanganate in an aqueous acidic medium. Due to the deficiency and cost of the oxidant as well as the formation of large amounts of toxic wastewater, the known method has no future. Therefore, an urgent task is to develop a new, low-waste synthesis of 2-chlorobenzoic acid using the available and ballastless oxidant – ozone. The kinetics and mechanism of the liquid-phase oxidation reaction of 2-chlorotoluene with ozone are studied. It was found that the oxidation of the substrate with ozone occurs mainly in the aromatic ring with the formation of aliphatic peroxide compounds. Increasing the temperature to 90 °C and introducing the catalyst – cobalt (II) acetate – into the system contributes to an increase of oxidation selectivity by the methyl group from 18.0% to 92.5 %. Among the aromatic products, 2-chlorobenzoic acid (88.0 %) and 2-chlorobenzaldehyde (4.2 %) are formed.The aim of the work is to study the kinetics, the mechanism of the liquid-phase oxidation reaction of 2-chlorotoluene with ozone and to develop a new method of 2-chlorobenzoic acid synthesis basing on the research performed.Materials and methods. Glacial acetic acid manufactured by Sigma, “Ch. P.” qualified; 2-chlorotoluene, 2-chlorobenzaldehyde, 2-chlorobenzoic acid manufactured by company Acros organics company, “Ch. P.” qualified; cobalt (II) acetate, “Ch. P. qualified” were used in the experiments. Studies of the reaction mass quantitative composition were performed by gas-liquid chromatography. 2-chlorobenzoic acid was determined with potentiometric titration. Ozone concentration at the reactor inlet and outlet was determined by the absorption spectrophotometric method in the range of 254–290 nm on a SF-46 spectrophotometer designed to measure the transmission coefficients of liquid and solid transparent substances in the spectral range from 190 nm to 1100 nm.Results. The kinetics and mechanism of the liquid-phase oxidation reaction of 2-chlorotoluene with ozone have been studied. It was found that raising the temperature to 90°C and introducing a catalyst – cobalt (II) acetate – into the system results in an increase in the selectivity of oxidation by the methyl group from 18.0 % to 92.5 %. Among the aromatic products, 2-chlorobenzoic acid (88.0 %) and 2-chlorobenzaldehyde (4.2 %) are formed.Conclusions. During the oxidation of 2-chlorotoluene with ozone in acetic acid, mainly aliphatic peroxide compounds are formed, and 2-chlorobenzoic acid is formed only with a yield of 16.5 %. Increasing the temperature to 90 °С and introducing cobalt (II) acetate into the catalyst system makes it possible to direct the process mainly to the methyl group with the formation of 88.0 % 2-chlorobenzoic acid.

OXIDATION PRODUCTS OF ETHYLBENZENE AND ITS SUBSTITUTED BY OZONE IN ACETIC ACID

Based on the obtained kinetic regularities and the mixture of the products of the reaction of ethylbenzene oxidation with ozone in acetic acid, the scientific bases of the technology of synthesis of acetophenone was developed. It is shown that in the ozonation conditions, in the presence of manganese (II) acetate, it is possible to direct oxidation mainly through the ethyl group of the substrate with the formation of aromatic products. The technological parameters are studied and the optimal conditions for the process realization are ascertained. The obtained experimental and theoretical results allowed us to propose a new low-temperature low-waste method of acetophenone production, which ensures the efficiency of the process due to the mild oxidation conditions (288 K, atmospheric pressure) and the reduction of toxic waste. The technology can be an alternative to existing methods of the synthesis of aromatic ketones.

Kinetics of catalytic oxidation 4-bromethylbenzene by ozone in acetic acid

The kinetic regularities of catalytic oxidation of 4-bromoethylbenzene by ozone to create an eco-logical, low-temperature technology for the synthesis of 4-bromoacetophenone have been studied. The experiment was performed in a glass reactor with a porous membrane under conditions of kinetic regime at a temperature of 293-333 K. The concentration of ozone in the gas phase was determined by spectrophotometric method. Analysis of 4-bromoacetophenone and its oxidation products was performed by gas-liquid chromatography. Oxidation of 4-bromoethylbenzene by ozone in a solution of acetic acid at a temperature of 293 K in the presence of catalytic impurities of manganese (II) ace-tate proceeds mainly on the ethyl group with the formation of a mixture of 4-bromoacetophenone (95.6 %) and 1-(4-bromophenylethanoacetate 4.2 % ). Prevention of destructive oxidation of the ben-zene ring (ozonolysis) with the involvement of the catalyst is explained by the fact that ozone under ca-talysis mainly reacts with a salt of manganese (II) and not with the substrate to form the active form of manganese Mn(IV) which has high substrate selectivity to alkylarenes, directs the oxidation of 4-bromoethylbenzene to the ethyl group. High selectivity of side chain oxidation is achieved only at ele-vated catalyst concentrations, which is largely due to the higher reaction rate of the substrate with ozone than with Mn(IV). The composition of the products of catalytic oxidation of 4-bromoethylbenzene depends on the temperature: at 293 K the reaction stops at the stage of formation of the corresponding ketone and acylated alcohol, increasing the temperature promotes further oxidation of 4-bromoacetophenone to 4-bromobenzoic acid, thus forming a mixture containing 4-bromoacetophenone (82.5 %), 1-(4-bromophenyl)ethanolacetate (4.2 %) and 4-bromo-benzoic acid (11.8 %). The research allowed to formulate general regularities of the reaction of catalytic oxidation of 4-bromomethylbenzene by ozone in acetic acid, to explain the role of the catalyst in the system and to propose a chemical scheme of oxidation corresponding to experimental data.

Oxidation of 4­brometylbenzene by ozone in acetic acid

The kinetics and the mechanism of ozonation of 4-bromethylbenzene in acetic acid was studied. The constants of the rate of reaction of ozone with 4-bromethylbenzene and 4-bromacetophenone at different temperatures were determined. We showed the possibility of conducting the process not only by the aromatic ring of the substrate in accordance with the Krige mechanism, but also with the formation of 4-bromacetophenone, which will be used when creating new methods of synthesis of oxygen-containing derivatives of ethylbenzene. It was established that oxidation of 4-bromethylbenzene by ozone in acetic acid flows mainly by the aromatic ring with the formation of ozonides – peroxide products of aliphatic nature. Up to 35 % of 4-bromacetophenone and trace amounts of 1-(4-bromphenyl)ethanol were identified among the products of oxidation reaction by the side chain. The reaction of ozone with 4-bromethylbenzene in acetic acid at temperatures of up to30 °Chas the first order by initial components and the value of constant of reaction rate does not depend on the concentration of reactants. With increasing temperature, constant of reaction rate begins to depend on the concentration of reagents, and in this case, ozone consumption increases significantly. This indicates that under experimental conditions, ozone is consumed simultaneously at different stages of oxidation. It was proved that ozonation of 4-bromethylbenzene is a complicated process, in which the substrate is oxidized by the non-chain mechanism. Ozone is consumed in two directions: in the reaction with the substrate by non-chain mechanism and by the chain mechanism at the stage of chain continuation in the reaction with the products of thermal decomposition of ozonides. This fact gives grounds to argue that at an increase in temperature, unproductive consumption of ozone will grow rapidly and, vice versa, under conditions of prevention of ozonolysis, ozone will participate in the reaction with formation of the target aromatic product. Thus, the experimentally obtained data are the basis for the development of the process of oxidation of derivatives of ethylbenzene and creation of the foundations of technology of 4-bromacetophenone synthesis with the help of ozone. This will considerably simplify the apparatus design of the process, enhance the output of the target product and will contribute to subsequent improvement of the method of oxidative processing of reagents

Rapid Removal of Tetracycline (TC) by Ozonation after Extraction TC from Water into Acetic Acid Solution Using Granular Activated Carbon

This study quantifies the rapid removal of tetracycline (TC) in acetic acid solution by ozonation after extraction from water into acetic acid solution using granular activated carbon (GAC). Systematic laboratory experiments show that GAC can be used as an adsorbent to transfer TC from water to acetic acid. Ozone gas has a high degree of stability and solubility in acetic acid, and therefore apparently enhances the removal rate of TC. TC removal efficiency is better in 10% acetic acid solution than that in water, 15% and 20% acetic acid solution. Removal rate of TC in the acetic acid solution decreases as the initial molar ratio of TC and O3 increases. Inhibition effect of tertiary butyl alcohol (TBA) on TC removal is smaller in acetic acid than that in water. metal-TC complex was produced in the presence of Fe3+ and Co3+, which inhibited the degradation of TC by ozone in acetic acid. Removal of TC by ozone in the acetic acid solution might be affected by multiple factors, which should be considered in practical applications.

The oxidation of ethylbenzene by ozone in acetic acid

Reaction of ozone with ethylbenzene in acetic acid is studied. It is shown that oxidation of ethylbenzene by ozone develops in two directions: on double bonds of an aromatic ring with the formation of aliphatic peroxides and ethyl group with the formation of phenyl methyl carbinol and acetophenone. It is established that the main products of reaction are peroxide compounds - products of destruction of the aromatic ring (60% ) and, to a lesser extent, oxidation products on a side chain - acetophenone (25 %) and phenyl methyl carbinol (10 %). The constants of the rates of ozone reaction with ethylbenzene at various temperatures are defined, and the reaction mechanism, which explains the obtained experimental data is proposed.During the research, the concentration of ethylbenzene and products of its transformation in solution was determined by a method of gas-liquid chromatography on the chromatograph with flame ionization detector. The content of peroxide compounds was determined by iodometric titration. The constants of the rate of ozone reaction with ethylbenzene were calculated by the method described in the paper [2].

Catalytic oxidation of alkylbenzenes with ozone in acetic acid in the presence of strong acids

The oxidation of ethylbenzene with ozone in the acetic acid-sulfuric acid system in the presence of Mn(II) acetate and cumene in the acetic acid-trifluoroacetic acid system in the presence of Co(II) acetate has been studied. The main factors that affect the catalytic ozonation of alkylbenzenes are discussed. A redox catalysis mechanism is proposed. The kinetic characteristics of the main stages of the catalytic cycle have been determined.

Catalytic ozonation of alkylnaphthalenes in acetic acid

The oxidation of alkylnaphthalenes with ozone in acetic acid in the presence of cobalt(II) acetate is reported. Under the catalytic conditions, the ozonolysis of the aromatic system can be prevented to a considerable extent and the reaction can be directed toward the oxidation of the alkyl group. The kinetics of the main steps of the process is reported, and the mechanism of redox catalysis is presented.

Kinetics and products of the catalytic oxidation of acetamidotoluenes with ozone in acetic acid

The kinetics of acetamidotoluene oxidation in glacial acetic acid in the presence of cobalt acetate is reported. At 95°C and atmospheric pressure, acetamidotoluenes are oxidized by molecular oxygen very slowly: oxidation is complete in 10–12 h, and the major reaction products are acetamidobenzoic acids (27–36% yield). The introduction of ozone into the reactive gas increases the reaction rate by one order of magnitude. The main role of ozone is to generate the active form of the catalyst.

Oxidation of benzyl alcohol and benzaldehyde with ozone in acetic acid

Ozonation of benzyl alcohol and benzaldehyde in acetic acid was studied. A method for ozonation of these compounds is suggested.

Study of 4-acetylaminotoluene ozonation in acetic acid

The reaction of 4-aminotoluene with ozone in acetic acid was studied. It was found that the reaction proceeds at a high rate, giving predominantly tars. The product composition changes after acylation of the amino group: aliphatic peroxides prevailed among the oxidation products and 4-acetylaminobenzoic acid was identified (16%) as well. It was shown that the presence of a catalyst (cobalt(II) acetate) had no substantial effect on the oxidation selectivity for the methyl group (32%) and only the addition of potassium bromide increased the activity of the catalyst; the yield of 4-acetylaminobenzoic acid reached 70%. The mechanism of oxidation in the presence of a cobalt-bromide catalyst explaining the obtained results was discussed.

The first example of cobalt(III) μ-oxoacetate with water molecules in apical positions

Oxidation of Co(MeCOO)2·4H2O with ozone in acetic acid followed by the treatment with nitric acid results in the formation of the trinuclear oxo-centered acetate complex [CoIII 3(μ3-O)(μ-O2CMe)6(OH2)3] NO3·MeCOOH ([I]NO3·MeCOOH). Reasons of a decrease in the idealized symmetry of molecular structure (D 3h → D 3) of the complex cation [I]+ were analyzed by means of quantum-chemical calculations. The complex does not retain its structure in solutions (in water, methanol, and ethanol).

Oxidation of 4-aminotoluene with ozone in acetic acid solution

The possibility of preparing 4-aminobenzoic acid by oxidation of 4-aminotoluene with ozone in acetic acid in the presence of cobalt(II) acetate and potassium bromide was examined. The optimal oxidation conditions were found.

Oxidation of 2-methoxy-3,6-dichloropropenylbenzene with ozone

Oxidation of 2-methoxy-3,6-dichloropropenylbenzene with ozone in acetic acid and carbon tetrachloride was studied.

Oxidation of 2‐Methylnaphthalene with Ozone.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Development of a Method for Resist Removal by Ozone with Acetic Acid Vapor

A method of removing the photoresist using ozone gas with acetic acid vapor has been developed. Glass substrates (size mm2) coated with I-line resist were treated under the conditions of substrate temperature, 27-50°C; acetic acid vapor, 2-18 vol %; ozone, 0-9.3 vol % (0-200 g/m3); total gas flow rate, 2 L/min; and gas pressure, 100 kPa. A previous ozone treatment with oversaturated water vapor or sprayed water overcame the limitation of ozone diffusion into the resist by the control of the water film on the resist. In this study, pure acetic acid vapor has been first applied for the resist removal by ozone in order to improve the oxidation rate of the resist, because acetic acid is an inactive solvent in the ozonization, and the solubility of ozone is much higher than water. It was observed that the resist removal rate increased with acetic acid and ozone concentration, and reached at 6 μm/min at which was about six times greater than that of the previous ozone treatment. Metal corrosion of molybdenum and aluminum electrodes was found negligible during the ozone treatment with acetic acid vapor. The mechanism of resist removal without the metal corrosion by ozone with acetic acid vapor is also discussed, based on the solubility of ozone in acetic acid and the corrosion current in ozonized solutions. © 2004 The Electrochemical Society. All rights reserved.