Organic peroxide production in the Cl2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the Cl₂-ethane-air photoreaction system. Ethyl hydroperoxide (CH₃CH₂₁OOH, EHP) and peroxyacetic acid ( CH₃C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH₃OOH, hydroxymethyl hydroperoxide (HOCH₂OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH₂OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.     

Organic peroxide production in the Cl2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the Cl₂-ethane-air photoreaction system. Ethyl hydroperoxide (CH₃CH₂₁OOH, EHP) and peroxyacetic acid ( CH₃C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH₃OOH, hydroxymethyl hydroperoxide (HOCH₂OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH₂OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.     

Organic peroxide production in the Cl_2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the CI2-ethane-air photoreaction system. Ethyl hydroperoxide (CH3CH2OOH, EHP) and per-oxyacetic acid ( CH3C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH3OOH, MHP), hydroxymethyl hydroperoxide (HOCH2OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and MHP were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH2OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.     

The analysis of combustion products : The polarographic determination of the lower organic peroxides

Some lower alkyl and acyl hydroperoxides and dialkyl peroxides have been prepared and their $\text{built}\text{i}{}_{\mathrm{<mtext>d</mtext>}}\text{c}$ values and halfwave potentials have been determined. The halfwave potentials become successively less negative on passing from hydrogen peroxide up the series, the order beingH₂O₂, CH₃OOH, EtOOH, (CH₃)₃COOH, R-CO(OOH)The limiting diffusion currents have been shown to be proportional to the concentrations of individual peroxides, and to be additive in mixtures. Methods have been developed which permit the detailed analysis of mixtures of peroxides containing, for example, hydrogen peroxide, methyl-, tert.-butyl and acetyl hydroperoxides, and diethyl peroxide. The effect of aldehydes has been investigated.     

The kinetics of complex formation between Ti(IV) and hydrogen peroxide

The kinetics of the formation of the titanium‐peroxide [TiO²⁺₂] complex from the reaction of Ti(IV)OSO₄ with hydrogen peroxide and the hydrolysis of hydroxymethyl hydroperoxide (HMHP) were examined to determine whether Ti(IV)OSO₄ could be used to distinguish between hydrogen peroxide and HMHP in mixed solutions. Stopped‐flow analysis coupled to UV‐vis spectroscopy was used to examine the reaction kinetics at various temperatures. The molar absorptivity (ε) of the [TiO²⁺₂] complex was found to be 679.5 ± 20.8 L mol^?1 cm^?1 at 405 nm. The reaction between hydrogen peroxide and Ti(IV)OSO₄ was first order with respect to both Ti(IV)OSO₄ and H₂O₂ with a rate constant of 5.70 ± 0.18 × 10⁴ M^?1 s^?1 at 25°C, and an activation energy, E_a = 40.5 ± 1.9 kJ mol^?1. The rate constant for the hydrolysis of HMHP was 4.3 × 10^?3 s^?1 at pH 8.5. Since the rate of complex formation between Ti(IV)OSO₄ and hydrogen peroxide is much faster than the rate of hydrolysis of HMHP, the Ti(IV)OSO₄ reaction coupled to time‐dependent UV‐vis spectroscopic measurements can be used to distinguish between hydrogen peroxide and HMHP in solution. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 457–461, 2007     

乙烷/H2O/O2/N2体系中光致过氧化物的产生

采用长光路Fourier红外光谱(LP-FTIR)和高压液相色谱(HPLC)技术研究了乙烷/H2O/O2/N2光化学体系中过氧化物的产生，证实乙烷降解产物中有过氧化氢、乙基过氧化氢(CH3CH2OOH,EHP)和过氧乙酸[CH3C(O)OOH,PAA]，并首次发现了甲基过氧化氢(CH3OOH,MHP)、羟甲基过氧化氢(HOCH2OOH,HMHP)和过氧甲醚(CH3OOCH3,DMP).H2O2,MHP和EHP的最大计算产率分别为6.8%，6.4%和6.7%，是乙烷降解生成的主要过氧化产物。MHP主要来自乙烷降解过程中的中间物乙醛的光解。HMHP的检出表明乙烷降解过程中可能有Criegee中间体.CH2OO.产生。OH自由基引发的乙烷降解反应可能是对流层大气H2O2，MHP及EHP的重要来源之一。     

Determination of the isomerization rate constant HOCH2CH2CH2CH(OO·)CH3 →HOC·HCH2CH2CH(OOH)CH3. Importance of intramolecular hydroperoxy isomerization in tropospheric chemistry

The rate constant of the title reaction is determined during thermal decomposition of di-n-pentyl peroxide C₅H₁₁O( )OC₅H₁₁ in oxygen over the temperature range 463–523 K. The pyrolysis of di-n-pentyl peroxide in O₂/N₂ mixtures is studied at atmospheric pressure in passivated quartz vessels. The reaction products are sampled through a micro-probe, collected on a liquid-nitrogen trap and solubilized in liquid acetonitrile. Analysis of the main compound, peroxide C₅H₁₀O₃, was carried out by GC/MS, GC/MS/MS [electron impact EI and NH₃ chemical ionization CI conditions]. After micro-preparative GC separation of this peroxide, the structure of two cyclic isomers (3S*,6S*)3α-hydroxy-6-methyl-1,2-dioxane and (3R*,6S*)3α-hydroxy-6-methyl-1,2-dioxane was determined from ¹H NMR spectra. The hydroperoxy-pentanal OHC( )(CH₂)₂( )CH(OOH)( )CH₃ is formed in the gas phase and is in equilibrium with these two cyclic epimers, which are predominant in the liquid phase at room temperature. This peroxide is produced by successive reactions of the n-pentoxy radical: a first one generates the CH₃C·H(CH₂)₃OH radical which reacts with O₂ to form CH₃CH(OO·)(CH₂)₃OH; this hydroxyperoxy radical isomerizes and forms the hydroperoxy HOC·H(CH₂)₂CH(OOH)CH₃ radical. This last species leads to the pentanal-hydroperoxide (also called oxo-hydroperoxide, or carbonyl-hydroperoxide, or hydroperoxypentanal), by the reaction HOC·H(CH₂)₂CH(OOH)CH₃+O₂→O()CH(CH₂)₂CH(OOH)CH₃+HO₂. The isomerization rate constant HOCH₂CH₂CH₂CH(OO·)CH₃→HOC·HCH₂CH₂CH(OOH)CH₃ (k₃) has been determined by comparison to the competing well-known reaction RO₂+NO→RO+NO₂ (k₇). By adding small amounts of NO (0–1.6×10¹⁵ molecules cm⁻³) to the di-n-pentyl peroxide/O₂/N₂ mixtures, the pentanal-hydroperoxide concentration was decreased, due to the consumption of RO₂ radicals by reaction (7). The pentanal-hydroperoxide concentration was measured vs. NO concentration at ten temperatures (463–523 K). The isomerization rate constant involving the H atoms of the CH₂( )OH group was deduced: or per H atom: The comparison of this rate constant to thermokinetics estimations leads to the conclusion that the strain energy barrier of a seven-member ring transition state is low and near that of a six-member ring. Intramolecular hydroperoxy isomerization reactions produce carbonyl-hydroperoxides which (through atmospheric decomposition) increase concentration of radicals and consequently increase atmospheric pollution, especially tropospheric ozone, during summer anticyclonic periods. Therefore, hydrocarbons used in summer should contain only short chains (<C₄) hydrocarbons or totally branched hydrocarbons, for which isomerization reactions are unlikely. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 875–887, 1998     

Cholesterol Peroxidation as a Special Type of Lipid Oxidation in Photodynamic Systems

Like other unsaturated lipids in cell membranes and lipoproteins, cholesterol (Ch) is susceptible to oxidative modification, including photodynamic oxidation. There is a sustained interest in the pathogenic properties of Ch oxides such as those generated by photooxidation. Singlet oxygen (¹O₂)‐mediated Ch photooxidation (Type II mechanism) gives rise to three hydroperoxide (ChOOH) isomers: 5α‐OOH, 6α‐OOH and 6β‐OOH, the 5α‐OOH yield far exceeding that of the others. 5α‐OOH detection is relatively straightforward and serves as a definitive indicator of ¹O₂ involvement in a reaction, photochemical or otherwise. Like all lipid hydroperoxides (LOOHs), ChOOHs can disrupt membrane or lipoprotein structure/function on their own, but subsequent light‐independent reactions may either intensify or attenuate such effects. Such reactions include (1) one‐electron reduction to redox‐active free radical intermediates, (2) two‐electron reduction to redox‐silent alcohols and (3) translocation to other lipid compartments, where (1) or (2) may take place. In addition to these effects, ChOOHs may act as signaling molecules in reactions that affect cell fates. Although processes a‐c have been well studied for ChOOHs, signaling activity is still poorly understood compared with that of hydrogen peroxide. This review focuses on these various aspects Ch photoperoxidation and its biological consequences.     

Role of Hydrogen Migrations in Carbonyl Peroxy Radicals in the Atmosphere

Carbonyl peroxy radicals (RC(O)O₂) are the ubiquitous radical intermediates in the atmospheric oxidation of volatile organic compounds. In this work, theoretical studies are carried out to explore the role of the unimolecular H-migration in the carbonyl peroxy radicals by using quantum chemistry and kinetics calculations. The results showed that H-migration could be significant in the atmosphere at least in CH₃CH₂CH₂C(O)O₂ and (CH₃)₂CHCH₂C(O)O₂ with rates of ∽0.012 and ∽0.58 s^?1 at 298 K. Subsequent reactions of CH₃CHCH₂C(O)OOH would lead to the products with multi-functional groups, which might affect the aerosol formation process; while (CH₃)₂CCH₂C(O)OOH would transform to formaldehyde and acetone in a few steps. These processes would be important for the atmospheric modelling of volatileorganic compounds under low-NO_x conditions.     

The rate coefficient for the reaction of O(3P) with CH3OOH at 297 K

The absolute second-order rate coefficient for the reaction, O(³P) + CH₃OOH → products, was measured to be ??₁ = (1.06 ± 0.26) × 10^?14 cm³ molec^?1 s^?1 at 297 K, where the quoted error is 2σ including precision and estimated systematic errors. The possible presence of (CH₃CH₂)₂O in our sample of CH₃OOH leads to a large error in ??₁ which reflects the relatively large uncertainty indicated. O(³P) was generated in excess CH₃OOH by photolyzing a small amount of O₃ at 532 nm, where CH₃OOH does not photolyze. The rate of removal of O(³P) in the experiments was monitored by resonance fluorescence detection. The increased reactivity of O(³P) with CH₃OOH relative to H₂O₂ is interpreted as due to H abstraction from the CH₃ group.     

Reaction of CH3O2 and HO2: Ab initio characterization of dimer structure and vibrational mode analysis for reaction mechanisms

All species involved in the multi‐channel reaction of CH₃O₂ with HO₂ have been investigated using density functional theory (DFT). The molecular geometries for various species are optimized employing the B3LYP method implementing the 6‐311++G** basis set. The relative energies of all species are calculated at the same level theory. The results show that there are two kinds of channels: singlet and triplet. The singlet channel involves four intermediates and six transition states. The triplet channel includes two intermediates and two transition states. There are four kinds of reaction products: CH₃OOH + ¹O₂, CH₃OH + O₃, CH₄ + 2O₂, and CH₃OOH + ³O₂. The vibrational mode analysis is used to elucidate the relationships of the intermediates, the transition states, and the products. The extensive investigation shows that the reaction mechanism is reliable. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Oxidation of white phosphorus by peroxides in water

A mixture of hypophosphorous, phosphorous, and phosphoric acids is formed during the anaerobic oxidation of white phosphorus by peroxides [ROOН; R = Н, 3-ClC₆H₄CO, (СН₃)₃С] in water. The rate of reactions grows considerably upon adding nonpolar organic solvents. The activity series of peroxides and solvents are determined experimentally. NMR spectroscopy shows that the main product of the reaction is phosphorous acid, regardless of the nature of the peroxide and solvent. A radical mechanism of oxidation of white phosphorus by peroxides in water is proposed. It is initiated by the homolysis of peroxide with the formation of НO^? radicals that are responsible for the homolytic opening of phosphoric tetrahedrons. Further oxidation and stages of the hydrolysis of intermediate phosphorus-containing compounds yield products of the reaction.     

A theoretical study of the reactions of carbonyl oxide with water in atmosphere: the role of water dimer

Carbonyl oxide is a well-known intermediate formed in gas-phase reactions of ozone with alkenes. Secondary reactions of carbonyl oxide are suggested to lead to the formation of HO, H₂O₂ and organic peroxides in the atmosphere. We performed a theoretical study of reactions of carbonyl oxide with water and a water dimer. Using CCSD(T)/6-311+G(2d,2p)//B3LYP/6-311+G(2d,2p) calculations we found that the most energetically favourable channel is the formation of hydroxymethyl hydroperoxide (HMHP) as the result of reactions of carbonyl oxide with the water dimer. The potential importance of water dimer reactions in the chemistry of the troposphere is discussed herein.     

Kinetics of the Selective Reduction of NO with CH4 Over an In-Fe2O3/HZSM-5 Catalyst

A kinetic model presented for the selective reduction of NO with CH₄ over an In-Fe₂O₃/HZSM-5 catalyst by considering the process as a combination of two simultaneous reactions: NO+O₂+CH₄ (reaction 1) and O₂+CH₄ (reaction 2). Linear regression calculation was employed to find the kinetic parameters. It was found that although the activation energies of the two reactions were almost identical, the reaction rate constants were dramatically different, namely, k₁k₂, indicating that the NO+O₂+CH₄ reaction was more preferable to take place on the In-Fe₂O₃/HZSM-5 catalyst as compared with the O₂+CH₄ reaction.     

Thermochemical kinetics of bromine nitrate,bromine nitrite,halogen hydroperoxides,dichlorine pentoxide,peroxycarboxylic acids,and diacyl peroxides

Heats of formation of BrONO₂, BrONO, BrOOH, FOOH, FOOCl, CF₃C(O)OOH, HC(O)OOH, CH₃C(O)OOH, and [CH₃C(O)O]₂ are estimated from bond contributions taken from J. Phys. Chem., 100, 10150 (1996). They agree within ±2 kcal/mol with recent experimental or ab initio data. The resulting BDE(O(SINGLEBOND)O)=36 kcal/mol value in diacetyl peroxide requires the concerted assistance of exothermic C(SINGLEBOND)C(O) weakening in the transition state of its decomposition into free radicals. It also implies the existence of a previously unrecognized 12 kcal/mol nonbonded repulsion in acyl anhydrides. The formation of chloryl chlorate with ΔH_f(O₂ClOClO₂)=50 kcal/mol, a marginally stable species toward dissociation into (ClO₃+OClO), may account for observations made in the [O(³P+OClO] system at low temperatures. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 41–45, 1998.     

Dimethyl carbonate: an environmentally friendly solvent for hydrogen peroxide (H2O2)/methyltrioxorhenium (CH3ReO3, MTO) catalytic oxidations

Environmentally friendly oxidations of various organic compounds with the hydrogen peroxide (H₂O₂)/methyltrioxorhenium (CH₃ReO₃, MTO) catalytic system have been described in dimethyl carbonate (DMC), a cheap commercially available and benign chemical having interesting solvating properties, low toxicity and high biodegradability. Oxidations proceeded with good conversions and in good yields. Spectrophotometric analysis demonstrated that the [CH₃ReO(O-O)₂] complex was formed in DMC and that it was stable for several days at room temperature.     

立方Nd2O3上过氧物种光诱导生成的18O同位素示踪考察

采用原位显微Raman光谱和¹⁸O同位素示踪技术,以325 nm激光为激发光源,对立方Nd₂O₃上过氧物种的光诱导生成过程进行了详细表征,进一步证实过氧源于分子氧对晶格氧的氧化反应. 结果还表明,325 nm激光在室温下即可诱导过氧的生成,在实验条件下,生成的过氧物种可与Nd₂O₃的晶格氧发生快速的氧交换反应,位于Nd₂O₃体相的晶格氧也可迁移至样品表层进而参与过氧的生成. 325 nm激光照射有助于促进晶格氧的迁移以及晶格氧与分子氧之间的氧交换反应.     

A Detailed Insight into the Effects of Morphologies of Cerium Oxide on Fenton-like Reactions for Different Applications

As an exceptional Fenton-like reagent, cerium oxide (CeO₂) finds applications in biomedical science and organic pollutants treatment. The Fenton-like reaction catalyzed by CeO₂ typically encompasses two distinct processes: one resembling the classical Fenton reaction, wherein cerium (Ce³⁺) triggers the decomposition of hydrogen peroxide (H₂O₂) to yield reactive oxygen species (ROS), and the other involves the complexation of H₂O₂ on the Ce³⁺ surface, leading to the formation of peroxides. However, the influence of diverse CeO₂ morphologies on these two reaction pathways has not been comprehensively explored. In this study, CeO₂ exhibiting three typical morphologies, rods, cubes, and spheres, were prepared. The generation of ROS and peroxides was evaluated using the 3,3,5,5-tetramethylbenzidine (TMB) oxidation reaction and the reduction current of H₂O₂, respectively. Moreover, the impacts of pH variations and CeO₂/H₂O₂ concentrations on the production and conversion of these two reaction products were investigated. To corroborate the distinctions between the resultant products and their applicability, apoptosis assays and acid orange 7 (AO7) degradation analyses were performed. Notably, CeO₂ rods exhibited the highest proportion of Ce³⁺, predominantly engaging in complexation with H₂O₂ to foster peroxide formation, thereby facilitating the robust degradation of AO7. However, the generated peroxides appeared to occupy Ce³⁺ sites, thereby impeding the H₂O₂ decomposition process. Conversely, Ce³⁺ species on the surface of CeO₂ cubes were primarily involved in H₂O₂ decomposition, leading to heightened ROS production, and thus showcasing substantial potential for damaging A549 tumor cells. It is worth noting that the ability of these Ce³⁺ species to form peroxides through complexation with H₂O₂ was comparatively reduced. In summation, this study sheds light on the intricate interplay between distinct CeO₂ morphologies and their divergent impacts on Fenton-like reactions. These findings expand our comprehension of the influences on its reactivity of CeO₂ morphologies and open new insights for applications in diverse domains, from organic dye degradation to tumor therapy.     

Persulfate and perphosphate oxidation of 2-propanol: A relative rate study

A competitive reaction study for two isoelectronic peroxides (peroxodisulfate S₂O and peroxodiphosphate P₂O) interacting with the free radical ·Clpar;CH₃)₂OH is described. The radical formation is initiated by photolysis, the amounts of peroxide remaining analyzed volumetrically. It is found that persulfate reacts with the organic radical over 100 times more rapidly than does perphosphate. Mechanistic consequences in relation to previous work are briefly discussed.     

Decomposition of alkyl hydroperoxide by a copper(I) complex: insights from density functional theory

The B3LYP theory and scaled hypersphere search method are utilized to explore pathways of (HO)₂PS₂Cu-mediated CH₃OOH decomposition, a model reaction of alkyl hydroperoxide with cuprous dialkyldithiophosphate [(RO)₂PS₂Cu]. It is found that the decomposition of CH₃OOH mediated by the copper(I) complex may lead to formaldehyde and water molecules via O-O bond heterolysis and subsequent intramolecular hydrogen transfer, with retainment of the copper(I) complex. The subsequent hydrogen transfer event and formation of water may add new understanding to the (RO)₂PS₂Cu-mediated decomposition process of alkyl hydroperoxide. The oxygen transfer from CH₃OOH to (HO)₂PS₂Cu moiety, as an O-O bond cleavage manner of CH₃OOH, is also found to occur.